I just used a black one in this quilt, and that was mostly on the darker fabrics too. For the sashing, I used that turquoise quilting marker.
So you've used that combination on quilts with washable marker in them? Fantastic, that's exactly what I needed to know! Do you put in laundry liquid as well?
What's meant to happen with the red and orange ones? I'm going to be making a yellow wholecloth quilt soon, with deep pink thread, so red or orange would have been the most obvious colour to mark it with. Especially since I'd prefer to use something I can iron so that I can mark up the quilt before basting, and according to my scrap tests, you can iron over those washable markers and they still wash out. (Of course, I will check this a lot more carefully, and should probably start some test pieces now to see whether leaving them around for a few months causes the colour to set.)