I think blood colors are caused by pigments in the blood. I don't have a good idea of what pigments (this is sort of based on an old theory/headcanon that its metals but that doesn't feel like it would right), but it outweighs the red of the natural blood color to color it. This makes green blood darker and (barely) thicker than say, fuscia or burgundy bloods, which need way less pigment to color. Mutant bloods (like karkat) have no pigment in their blood. Blood color is sort of a spectrum, because the pigments are combined to make the 11 main blood colors, with the exception of fuscia. This means most trolls have different shades of blood, but usually they don't stray from the definable blood colors. They can though! Fuscia bloods are treated differently, though. Fuscias aren't as rare as it seems, although they are rare. When a fuscia is hatched, she needs to have a specific color, or she'll be culled. The pigments in the blood color specific things, like tears, spit, and eyes, which means in mutants those things are clear, and the eyes remain grey. In the context of god tier, mutants don’t have visible wings because theres no blood pigment to color them. This is the same reason humans don’t have visible wings. Each caste comes with different things, but most of its variable. Bronzes are known for talking to animals, but its pretty common for burgundies to be able to as well, for example. Some features are caste specific, or extremely uncommon in other castes, like gold bloods having special eyes with their psionics, or ceruleans having. special eyes also.
I’m dubious on mostly gender specific castes like jades. the only way I can think to justify that is some form of blood based, sexual dimorphism, where cis male jades wouldn’t be jade at all but. thats kinda dumb i think. And there's no other caste to work for that. Also, that would imply there wouldn’t be any amab jades and I don’t think thats the case either (and would take away some interest too, implying every jade is afab). I DO think it could work for fuscias, as an extremely regulated caste, they just wouldn’t allow any amab grubs through. But then there’s also the dubious nature of assigning gender to trolls at all. Even if you could after (which is vaguely implied not to be the case immediately but I’m not getting into troll genitals), I don’t know what sexual dimorphism grubs would have, if any. Maybe gender could be decided based on what lusus chooses it? I've always thought that it would go the other way around, that the lusus's gender would be ambiguous, and would follow the troll's gender, but I think it could work both ways. A lusus chooses a troll, that's the gender they're assigned, and then if the trolls gender changes, so does the way they would refer to their lusus (if they want to). Maybe for some trolls, their lusus is sort of a. I can't think of the right word. Their lusus could out them, if it looked wrong. I'm getting off track. That's all actually.