I've said it before, I say it a lot honestly, but I love the reasonable assumptions we can make about firelizards breeding and social habits based on what we see in primarily DragonsDawn.
Like, we've got the basic 'greens Rise a lot and don't tend their nests while golds Rise more rarely and fiercely tend their nests'. That's great, we love us some behavioral morphs in species. But then you also have to consider what would lead to such a thing, namely that both of these behaviors have to be successful, and successful in comparison to each other, in order for one to not completely take over from the other. Meaning that each option has benefits over the other.
For instance, in years or seasons where there's a large predator population, gold clutches are probably the most successful as they're the best guarded. But if you're dealing with horrible weather, or gods forbid a Pass, the fact green clutches are spread out far and wide means it's more likely one or more will survive, while a gold needs just one bad storm or Fall to wipe her whole year's breeding opportunities off the map.
But like, the most obvious one is a pure numbers game. If you don't invest in your eggs post-laying, that frees you up to get back into laying condition sooner and make more eggs. For instance in emus you'll see a female lay 5+ eggs in a single nest, but then she leaves that business to the male and runs off to eat well and find another guy to foist eggs on, ending up with sometimes even five nests in a season. But if you do invest in your eggs post-laying, you get more security in-so-far as assuring your eggs hatch. In emus the males do that, they get the best of both worlds there, but even more effective is to have multiple individuals looking out for the eggs.
Which is where their eusocial-style behavior comes in! By having the rest of the group dedicated to supporting the gold as she guards and tends her nest, the cost of nest tending is spread out, reducing the load on any one member of the group. The same thing happens with youngcare, which seems to be wholly communal, again reducing the cost for any individual member of the group. But eusocial behaviors are most efficient when members of a group are related, you don't want to waste your life raising young that don't share your genes.
Then you remember that firelizards form mental bonds at birth, bonds that they can break with no issue but that they can and do maintain throughout their lives. Taking this and the last paragraph into account, most likely collections of wild firelizards are mostly formed of sibling groups. Even if your bronze brother didn't catch the gold this year, helping with the clutch improves the odds he'll catch next year, and in the meantime you have plenty of opportunity with the greens.
This also probably plays into the fact they hum for all allied births. A green's nest doesn't get tended, but the young still need feeding at hatching. If you're a male then coming when you get the psychic 'birth here now' signals is an easy choice because there's the real chance these are your brother's offspring and his reproductive success is second only to your own. If you're a female, this nest is likely a sister's, in which case same deal, their success is only second to yours. On either side, having more babies around means a higher chance of any individual baby not being eaten by a predator, increasing the survival odds of your own children.
And then all this likely plays into the various male morphs and the color and size differences between ranks. I've mentioned elsewhere- the various male morphs are likely optimized to chase different female morphs. Blues can keep up with the quicker, more agile greens, bronzes with the slower, longer flying golds, and browns are a 'jack-of-all-trades' rank that doesn't specialize but instead can successfully chase either female morph, just with lower odds than the specialized males.
As far as size differences go, it's again all on the females to start. Golds lay larger clutches and defend them from things like wherries, they need to be larger to fit more eggs, to better defend their nests, and to drive off rival golds. Bronzes have to be large to keep up with the golds when they Rise. Greens specialize in laying more clutches and so likely smaller clutches, so they don't need to get as big and can instead focus on evading predators and even being able to lure predators from a freshly laid clutch without getting snatched up, small size is useful there. Blues are also small because it allows them the speed and maneuverability to chase greens. Presumably the reason they're larger than greens are is due for some reason to their being male, likely related to the complex genetics likely tied to rank*. Browns are in the middle because it allows them enough speed and maneuverability to go for greens, but also enough stamina to try for golds.
Color, meanwhile, is likely a camouflage thing. Blues, greens, and browns are all natural colors, perfect for making it harder for predators to notice you. According to the DLG firelizards come in a variety of shades, I wouldn't be surprised if there was even a degree of midtones between the various ranks. Golds and bronzes, meanwhile, I think are more likely a matter of reflective camouflage. A gold on a nest may be hard to look at in bright light, or at a glance appear to just be a patch of wet sand. If a gold has to leave the nest, more likely the sire would be left to guard it, and similar camouflage would fill a similar role. It might even, for some bronzes, give the impression that the larger gold is still on the nest, deterring predators that don't want to tangle with one. Since the smaller ranks are far less likely to be on a nest, more matte tones to mack dirt, wood, sky, foliage would be most effective.
It's all just fascinating and not quite like anything we have on Earth, though you can make parallels between several different Earth species. Absolutely love it.