Looks like great fun, Kat. I love playing around with colours. Please show us when you've finished. I wouldn't presume to impose my ideas because colour is such a personal thing. There's something to be said for following your first idea I always think. I love yellow. I never have enough around me. Clear yellows --not muddy ones - lemon yellow to buttercup to sunshine and all in between. On the other hand I know most people feel more comfortable with green. A monochromatic scheme using green would give you lots of scope. I really like your Tree of Hearts. Looking forward to seeing how it goes.
Cheers, Joy