Change Colors on Computer Generated Art Files

I have 40 PNG computer generated art files that I need the colors changed in several different combinations. I would like at least 5 different aesthetically pleasing color combinations per image. (Each image can utilize the same color combinations.). You will be asked to create at least 20 different color combinations of one image as part of the selection process to be contracted for the rest of the job. Final images must be delivered in highest quality. An example image is provided below.