Thanks to everybody for the suggestions and sorry that I took this much to reply, but I am having some nasty hardware problems. Fortunately I will be getting a new PC soon to continue my work on Crei.

I used those colors to better separate them on gray scale. Also, because I do not know a better technique to differentiate grasslands/plains from highlands/crops from jungles/forests from lowlands/swamps from mountains. I personally do not like the way how most (if not all) of the pre-made icons i have seen so far look.