I rent an old bungalow an the whole upstairs is painted a neutral light grey? I thought about painting it but my fabric covers all the walls, but what I did was I made a very small valance for my large sliding windows, its 10" tall by the length of the window an its a very abstract print with all the colors of the rainbow on it, it's just enough to brighten the room, and also represents all the colors in my fabrics that I use. Although I think yellow is a nice sunny color, you don't have to go real bright on it, I think it would work out ok, white is good too, but I really like alot of natural light from the window.