You can use acrylic felt to create a color in trapunto on a whole-cloth quilt. Karen McTavish uses it...a red to create a pink when seen through the whole-cloth, etc. It is really fun to use under white or light colored material in a quilt to come up with a completely different color. It definitely needs to be washed first if you are going to use it in a whole-cloth quilt since the quilt will need to be soaked to remove all quilting markings after it has been quilted...you for sure don't want to have bleeding through on a quilt like that. I would only use it on a wall-hanging or a show quilt that won't be washed often, if at all.