Your rug question is a tough one! First, I'd make sure the rug is a natural fiber. (My guess is it's probably wool.) Natural fibers will take dye; un-natural fibers may or may not. Usually not. Or at least not well. The other thing is I'd only attempt this on a rug that I don't mind tossing out if it doesn't work! So, that being said, if I attempted this, I'd take the rug outside and lay it right side up on a piece of plastic sheeting or an old tarp. Then I'd get a spray bottle filled with pre-mixed Rit and spray it down. The trick would be to spray repeatedly and evenly. The dye probably wouldn't be able to hide all the patterns of the rug, so they'd show up light or dark or whatever. It sounds tricky to me, but I could work. Did you by any chance see my painted rug post? If cost is an issue, this might be an alternative. The rugs are really cheap; my whole project--rug and paint--cost about 14 bucks. The project rug was a stone color, but they come in grey as well. You could finish the edges with a different shade of grey for a tone on tone look. Just a thought.....!