We all know that the Silver Eyes are important. But what if there's something more... important to eye colors in the RWBY universe? What if, in fact, each eye color has its own association? Below I have gathered a list of all known characters by eye color, and seek to theorize on what they could possibly mean. Granted, in cases of inconsistency, I went with the most common eye color portrayed--except where I think that inconsistency is actually supposed to mean something. Also, I only went with named characters.
Ah, the ever popular blue-eyed beauty. Nine characters have this--well, thirteen, if one counts the Schnees. They're a special case, though, so let's stick with the nine we know about for now: Cardin Winchester, Ciel Coliel, Dove Bronzewing, James Ironwood, Jaune Arc, Nadir Shiko, Neptune Vasilias, Sun Wukong, and Taiyang Xiao Long.
Quite the spread there. Might be difficult to find commonalities...
...but. Jaune says he's from a long, famous line. Ironwood, well, he's head of an academy--and a military--so it wouldn't be too strange to assume he might have connections, familial ones possibly. In fact, all the people on this list are both fighters and have a link to commanding--either being leaders, or having leader-associated traits--Dove's skill in analyzing other mid-combat, Neptune's charisma, Taiyang's care for his subjects (daughters). In fact, the only exception is Nadir Shiko...
...and Nadir's eyes are tinged grey. In fact, Winter Schnee's eyes are also tinged grey, in stark contrast to the icy blue of her father and her siblings. And looking at an old photograph of Taiyang shows that his eyes appear more lilac--akin to his daughter's--although that could, perhaps, be passed off as photographic imperfections.
Still, there's evidence that eyes in the RWBY verse could change color over time, perhaps as a reflection of the personality behind them. If blue eyes represent command, leadership, and honor, then perhaps Nadir and Winter are fading from that particular type of thought. It might also explain why the Schnees are their particular shade of blue--they've only become leaders recently, and don't quite have the honor yet to stand up with those who have had leadership in their family line for a while.
Tied with green eyes for the most examples, we've got Amber, Bartholomew Oobleck, Bolin Hori, Coco Adel, Flynt Coal, Gwen Darcy, Hazel Rainart, Junior Xiong, Ozpin, Peter Port, Russel Thrush, Sky Lark, Tukson, and Velvet Scarletina. And also Oscar, but I'm ignoring him for the moment, he's a special case.
Wow, you thought Blue was a wide spread, here's fourteen people...
Now there are a number of "ordinary" individuals in this list. But there's also a number of movers and shakers. Still, there are some commonalities--the shakers are all demonstrated to care for those under them, and the ones that don't lead appear to follow their leaders with no hesitation. It might be best to call these fellows the "supporters;" they may be awesome on their own, but their true passion lies in helping others be awesome.
An interesting note: Bolin Hori's eyes might be brown, but they're also gold-tinged, which leads us pretty nicely into the following list...
Well, gold or amber or yellow. I folded this all in a bit. Blake Belladonna, Cinder Fall, Corsac Albain, Fennec Albain, Ghira Belladonna, Kali Belladonna, Li Ren, Lisa Lavender, Sage Ayana, and (debateably) Tyrian Callows. With nine or ten examples, we've got quite a bit to go on.
First interesting note: This group has the largest number of Faunus. Granted, three of those are the Belladonnas, and the Albains are brothers (possibly twins), so there may be some family heritage going there. Still, even if we only marked them as two, that's two more then the brown group, so something must be going on here.
And what do we know of these particular Faunus? Blake likes to read. Ghira founded a resistance movement. Corsac and Fennec are well skilled in the art of wordcrafting. Kali... likes to hear about adventures. And Tyrian has a poetic side to his madness. Compare that to Lisa being a reporter, Cinder being a schemer, and Li Ren giving his son very important advice--note that Li's eyes are brown-tinged, and we've gone over what that means...
I think it's safe to say that the golden-eyed are thinkers, intellectuals, people who could have be writers and artists... on top of being warriors. Interestingly, Sage Ayana's eyes are tinged green...
Our second fourteen-person group, with Arslan Altan, Arthur Watts, Glynda Goodwitch, Melanie Malachite, Mitiades Malachite, Nebula Violet, Neon Katt, Octavia Ember, Penny Polendina, Pyrrha Nikos, Reese Chloris, Roman Torchwick, Roy Stallion, and Scarlet David. And Oscar, again, but he's a special case, come back to him later.
Well this is an interesting collection. Especially since Arslan Altan, Nebula Violet, and Octavia Ember have gold-tinged eyes.
Let's go over what we know of the ones we know about--Glynda, Penny, and Pyrrha are all very technical in their combat. Neon might seem lackadaisical, but she never misses a beat. The Malachite twins are quite a couple of dancers in their fights, Roman has a flair for the dramatic, and doctor Watts... he dislikes failure. It might be less pronounced in the other green-eyed characters, due to their lack of screentime, but...
...I think the green eyed ones are performers. Perfectionists. They devote themselves fully to whatever identity they craft, and... that can have downsides, in both Pyrrha's lack of sociability, and Penny's awkward nature, but there's something to be said for training and effort.
Grey and Silver Eyes
Yes, a group with two types! May Zedong, Mercury Black, Ruby Rose, Summer Rose, and Zwei. Yes, I am counting the dog here. And yes, I know Ruby and Summer explicitly have silver eyes, as opposed to just having gray eyes, but....
May is a sniper, and a good one at that, although we know little about her beyond that. She had a brief non-combat cameo in the season three opener, where we got to see her eyes were just slightly tinged with blue--just slightly tinged, approaching Winter's eye color from the other end. Mercury, well, he's a sociopath, quite willing and able to kill and injure. Ruby is perky, socially awkward, and can wallop Grimm and thugs like a master--one of her noted character flaws is a tendency to get into fights without thinking. And Zwei has been shown to be eager to join in combat. For whatever reason. We don't have much on Summer beyond family recollections, but she might well have had the same... love of combat.
Gray eyes are fighters, warriors, who may not initiate combat (although they sometimes do) but revel in it with a unique skill and flair. They're also the only group to canonically have explicit super powers (the silver eyes) although that doesn't preclude others having them as well; it might be that each eye color has a unique ability, but certain people have been actively suppressing that knowledge to keep civilization safe...
Pink and Purple eyes
Yes, another two for one combo! On the pink side we have An Ren, Lie Ren, and Nolan Porfiro; on the purple side we have Brawnz Ni, Dew Gayl, and sometimes Tyrian Callows. Technically we've also got Yang Xiao Long and her lilac eyes for purple, so we should touch on that. Three of those are Vytal Tournament one-offs, one of them is dead, so let's look at Ren, Tyrian, and Yang for now.
Ren is... interesting. Quiet, but that quiet stems from trauma. And behind it, he is helpful. He tries to give Pyrrha an energy smoothie, he considers Jaune to be a brother, and WOW he puts up with Nora. A lot. It might be best to assume that pink eyes are the color of the family tenders, the homemakers--not quite the same as brown eyes, who care for everyone, pink eyes are the people who care deeply. An Ren certainly showed that in her brief appearance. Granted, not enough data, but it fits.
Comparing Tyrian and Yang, you won't find a lot of commonalities, but there are two: both of them can swap eye color, and both of them throw themselves fully into whatever they do. Purple might very well be the color of passion, of feelings that run hot and hard, of the highest of highs and lowest of lows. This might be applied to old Taiyang, the one in the photograph--some of that survives to the current day, but if his eyes have changed to the blue of leadership it wasn't entirely his fault. The fact that two purple eyes can swap colors, one has changed, and the final two are Vytal one-offs... perhaps purple eyes are also the most volatile of personalities, leading them to incorporate other mindsets into themselves.
The show only provides us four examples of permanently red eyes: Emerald Sustrai, Qrow Branwen, Raven Branwen, and Salem. Yang Xiao Long sometimes has red eyes, but only when she activates her semblance... an interesting trait unique to her, as other characters activating their semblance doesn't actually change their eye color. It's actually pretty weird she's on this list, compared to the others....
Emerald is a thief who acts friendly to those she detests and can cause hallucinations. Qrow might be a drunk, but he's also got a versatile weapon and a tendency to distract others with 'shenanigans.' Raven is a bandit queen, which should mean she's a bad guy... but she's against the big bad, and there are hints she has quite a bit of moral ambiguity around her. Salem, of course, is the big bad... who works from shadows, through pawns, who manipulates her seconds with calm words.
Sneaks. Manipulators. The cunning, the hidden, the weavers in the dark. How could Yang fit into this? It's an interesting contradiction, until one realizes she does not broadcast her semblance--it's a surprise, if you're not expecting it, and she apparently didn't tell Blake about it until after she got blasted through a pillar--note how that girl was genuinely worried during the Atlas fight? Yang has just a touch of sneakiness to her--a side that she keeps hidden, only showing it when she needs to.
Let's go through this alphabetically, shall we?
Fox Alistair: Pure white eyes. Assumed to be blind. Has yet to speak. Covered in scars. A mystery....
Ilia Amitola: She seems to default to gray or silver eyes, but she's been seen with blue eyes. That she can deliberately control this only further confuses the issue; she may be well aware of the implications of each color and change her eyes (consciously or subconsciously) to match her emotional intent.
Klein Sieban: His default brown eyes play it straight, but the other eye colors he demonstrates are matched with personalities that seem to be slightly satirical versions of their matching color.
Neopolitan: Again, able to change her eyes on a whim. Seems to prefer brown and pink, but she's been seen with silver. Interestingly, she's never had both eyes pink at the same time.
Nora Valkyrie: Aha, thought I missed this one, did you? Nora's interesting in that her eye color varies A LOT. Enough so that the people over on TVTropes noticed. It seems to range between blue and green, getting greener the more time she spends in proximity to Ren. Factor in that we don't know much about her, and it may very well be our little Nora is actually a Valkyrie--or a fairy, or a changeling, or a robot or something. I would not be too surprised if the CRWBY pulled out some secret backstory for her.
Oscar Pine: The only case we know of where the eyes are dual-colored. Rare enough in reality, and also rare in fiction. Interestingly we only meet him after Ozpin's death, so it could well be a side effect of that--especially given his reluctance to leave the farm (green-eyed perfectionists, remember).
Taiyang Xiao Long: As previously mentioned, Taiyang's eyes are lilac in an old photo, and blue now. This could be attributed to the photo being old, or an animation error, or his eyes might actually have changed.
Tyrian Callows: Can swap eye color at will. Seems to do it when he's getting ready to poison somebody, might be connected to that. Not... exactly stable.
Yang Xiao Long: Can swap eye color when activating semblance. Notably, the only person who does! Yang's kind of complicated, emotionally.
Yatsuhashi Daichi: Skin-tone sclerae. Meditates before combat. Also mysterious.