Anything that dark will stain washcloths badly, no matter what you are using. Unless the hotel is supplying navy blue wash cloths and towels, I'd stick with white soap with the logo, or at most a colored wrapper. Laundry expenses trying to get the blue blotches off the white cloth is going to be a real problem!
Indigo is really bad about "staining" cloth because soap is fairly reduced chemically (as opposed to oxidized), and reduced indigo is both yellow-green and water soluble in alkaline solution. When it gets on cotton fibers, it will tend to stick, then turn blue and insoluble in the air as it oxidizes.
Bleach will slowly remove it (anyone remember bleached spots on their jeans when they were learning to do laundry?), but very heavy indigo color will probably still persist at the levels of bleach safe for the cloth.
Mica will be worse, as they cannot be bleached out, and charcoal will stain gray pretty permanently.