the easiest way to see color value is to use a piece of red film they used to make the old 3D glasses out of - it turns everything in to shades of reddish-gray and then she will see what you mean. Some of your quilting templates are that color and can be laid down on fabric to see what I am talking about. Or if you have some of those 3D glasses, just look out of the red side. As for color choices - buy a peep hole that you would put in a front door and look backwards through it. I have a child's kalediscope that I use to "see" what 1 square looks like as multiples. It helps a lot, too.