How can i change a moon's texture using core shaders? (and colors too-)

Previosly i asked for help to change a moon's texture and a night's lightmap using a command, i could figure the lightmap thing out using a core shader, but i don't know how to alter it's colors or even how it works, other than that, i was thinking if it was possible to change a moon's texture using a core shader, pls explain it because i have no idea how shaders work, and how could i even change the moon's texture using a core shader.. :(
also, about the colors, can you please explain how can i change them? because i don't know if it works on rgb, or any other color language. :/