This beta version seems set at the height of the dry season where grass and foliage colours will be more muted, but perhaps the overall saturation is a little low. The tarmac is also quite a light warm grey rather than a cooler darker one. I know someone commented about the dark tarmac in the dev thread at Assetto Corsa Mods which is maybe why it was changed, but I think I preferred the original darker, cooler grey. It added contrast and seems more true-to-life. Maybe the lighter, warm-grey tarmac is what's making you think the palette is a little bland?
A greener, more lush track skin could easily be done as a seasonal variation, and don't forget this is a beta release so final colours might still be under review. At the end of the day it's the modder's decision what final ambiance and atmosphere he wants to achieve.