Haha, I will no doubt get push back but as a photographer I highly encourage you to use a soft, light grey. Colors such as yellow, green, walls will reflect on your fabrics and projects and give you untrue colors. This might have some surprising outcomes if you pick your fabric choices in that room, sew it together and THEN see it in the light of day. IMHO of course. That is why photographers use/used grey cards when tweaking lighting, etc.