There's been an ongoing discussion about bark color. I spent a long time looking at pictures of palms and after extended discussion with horticultural experts (I emailed mr-miley this morning) it has been decided that they should be browner. (There's a huge range of colors and textures on palms. Date palms are a lot different than coconut palms, etc.) I got what I thought were pretty good results by changing the diffuse color on the trunks and stems from the current gray (191,191,191) to a light brown (168, 136, 78). Keep the same texture, just change the diffuse color mixed with it.