I wish I had a cool/helpful answer for that, but honestly I just looked really hard at my picture of her and tried to see the colors/imagine how they’d reflect with that bright background. My tip is to build up values by starting with a base color that’s complimentary/makes sense (in my case, a light blue) and then start making shapes. I brushed a wash coat of white over the yellows/blues/purples and then did highlights in the brightest colors for texture