I saw that ～を～とする means "as" and that 基調 means "to be the main color in something like a picture" (2nd definition), but I can't link everything in this sentence.
"Brown as white"? (Or is it "white as brown" because the wall was brown actually. I'll upload a picture). Should I consider it as "instead" instead of "as"? For example, "white instead of brown"...? Considering that there is both white and brown in the image, it looks the game is talking about both the colors, but I don't know which would be the main one.