A biome's rainfall value is typically a value from 0.0 to 1.0, and - as stated above - a biome's temperature starts at a given value at sea level (e.g. 2.0 for Desert or -0.5 for Cold Taiga) and decreases by 0.00166667 for each meter above sea level. Biome grass and foliage colors are selected from two 256x256 colormap images: grass.png and foliage.png.