well considering that plastic is porous I Imagine it will absorb the dye, and hot water just short of boiling (ie. boil it then let it cool for a few minutes) would open up the pores and allow more absorption of the dye (though could also warp it a little). the theory is sound, just not sure of how well it would actually work as far as how the color would actually look... ever seen a tie-dye? way brighter with the dye on the fabric til you rinse it out, then it just gets a little less dull... can't hurt to try it with something like a battery cover (you know the 360 AA holders) especially if you plan on painting it anyway...