I have spent the last 24 hours playing colour games. I have two great books on colour that I consult whenever I have such an exercise - "Colour Harmony Workbook" and Deb Menz's "Color Works". I particularly enjoy the latter because it is written for fibre workers.
I am not sure about the greens - I think I will use the yellow as the contrast.
Back to the needle and more practice on the hoop.