At this stage of a project I need to figure out what my colors are going to be. I know that my flowers are yellow, so that is my starting point. One of the things I have found helpful for color selection is to be able to refer to color combinations that I know work because they are in professional publications and well respected art work. If I come across a postcard, magazine advertisements, or some other printed piece with colors on it that appeal to me, I keep it and put it in a folder. Then I open that folder and refer to it when I am doing a new color plan for a painting or art quilt.
Above and below you see a grouping of postcards, fabric, magazine ads and articles, etc., all with a similar color combination. Those references all have a yellow that I like with warm sienna's, and blues. Those are the colors I want to use for this piece.
And below you see my sketch painted with those colors that I will use as my guide for my painting. I will have this up on my wall to use as a reference and have it handy when I am selecting fabrics.