Agatha was a pretty cool, if slightly weird, character wasn't she? Anyways, I think that you've done a really great with the background and I'm not sure what you mean about messing up the colours. Looks like you nailed them from where I'm sitting.
One thing that I would say, is that her nose is a little bit wonky. Did Link punch her when she demanded more bugs or something?
Her forearms and hands look a little flimsy as well, so you might want to watch out for that in future. She needs big hands to hold all those butterflies against their will!