If the prime criteria for color choice is for the true colors of the quilt you will be quilting to be not influenced by the wall color of your room, you might want to consider this. I remember once doing a color study for a weaving project. We were looking for a color to surround other colors so that the other colors would "pop" without being influenced by the red or the yellow or the blue in the outside color. Do you know what color worked beautifully?? A true grey!! White made colors looked washed out; black did not work for some colors--too stark; other colors influenced the tone or hue of the interior colors. So, perhaps you could use a soft pale grey . . . and use curtains and your quilting fabrics to provide the color we all crave.