The problem with dyeing/coloring, synthetics don't take color very well, and naturals; cotton, linen, etc.  may not hold up well over time, with coloring.   If coffee didn't work, it sounds like you are dealing with synthetic.   One of our sponsors, CraftySailor has some that looks good in the pictures..  Not sure how competitive they are, But I have had real good experience buying other products from them..     And don't forget:   Making your own ro