Have you tried a pale yellow a pale green or orchid? Perhaps one of these colors might work. Why not get a pad of all colors of construction paper the large sheets and put the prepared block on different colors to see what you might like. I realize that construction paper is not fabric, but you are checking out color. This might give you an idea of what color you might want to go with. What was your grandmother's favorite color, you might try that color and see how it does.