You dont need to clear it ^^
You can just lock the layer, you want to edit. Than you color it in. For ecample you want the Main Color to be brown, than you pick the color you like and over draw the existing color. Than you can set the markings and so can color it layerfor layer (you can find a list of layers that needed to be edited in the start-post)
Ah im sorry if im not good in explaining >o<
Dont know if
THIS can help you ^^
Best regards and thank you Sakura Kuromi