Civ color is always a challenge, but it is really important in my opinion.
I am working on something where civ color has also proven a real challenge. But I am gonna include reguardless. Sure it is a minor compromise, but not nearly as much of one as taking several weeks of modeling highly accurate and detailed bits and rendering the unit out at less than 100 pixels.
I am really excited to see more support for the islanders. I think they would make a very interesting addition to the game.
Great idea.
--edit--
possible civ color would be his loincloth, part of his sheild. A tassle on his spear, sandals, an arm or legband to hold the current tassles in place, and so on.
Also, didn't Civ's Army do a couple of islanders?? I am pretty sure he did a boat, and maybe more.