I have a thread in here where I used RGB lighting to illuminate the coin door reject button with a yellow happ reject button, and I got good results with the color. It wasn't perfect, but the yellow tint only really affected some of the colors. I can see how a green, red, or blue button would not react well to RGB, but the yellow one is not too bad. Of course I had a very bright LED setup too, which might make a huge difference.