Etching, staining, or wildly coloring plastic

I own too much plastic, that I use regularly, but want to decorate. Is there a SAFE method to chemically or otherwise "mottle" plastic with colors? Not looking to use paints, as those will just peel off. I know that plastics react to some solvents and such, but is there anything that you could 'wash' plastic with that would just outwardly alter the appearance? If I could get an "oil on water", or even just a "camo" sort of effect, that would be wonderful! (I tried searches for what to AVOID using around plastics without risking such an effect, but can't get the right search parameters...) Thanks for any ideas! I'd really prefer not to have to throw stuff out.