Colors in Songs Of Innocence and of Experience

I think that throughout the pictures so far in this novel that,the colors of the illustrations show the mood for the poem .For example in the poem Night he uses colors to represent the mood that he wants in the poem. When he has a dark and sad poem, he draws with dark colors like blues and deep reds. In his happier poems like Spring he uses yellows and oranges to show a happier mood for the corresponding poem.