Hey Amy...
To be quiet honest.. I am not sure either which over the counter colors contain metallic tints or which ones don't.. 
What I usually do though in CORRECTIVE COLOR CONSULTATION... Is EXPLAIN to the client.. that due to what they have done themselves at home.. prevents me from accomplishing what they want...
But I take it as serious as .. that I just assume that THEY(the store bought colors or box colors) ALL HAVE METALLIC AND VEGATABLE TINTS..
So to be quiet honest.. depending on what they want to achive... I tell them from the GET GO...
That unfortately due to that they colored it themselves.. that the color they used could and may have contained metallic dyes and vegatable tints.. which would prevent the hair from lifting... So depending what their end result is.. I will tell them unfortately they need to let it grow out.. then I make DO-ABLE suggestions..
Such as if the hair is say a funky orange color that got screwed up.. I suggest they can deposite color with no problems more or less.. just to achieve a even all over color..
If they have colored their hair the DREADED BLK... I suggest doing some highlights... to make it NOT SO BLK.. But let them know BLONDE HI-LITES IS OUT THE QUESTION.. Possiable.. darker to med brown at the most.. and if lucky could do maybe redish highlights.. or something along those lines..
Just some ideas.. of what ya could do... I always explain risk upfront..
and if the hair is already really dry.. I explain I refuse to do anything major like CORRECTIVE COLOR.. Until the hair is healthier to be able to take the chemicals.. safely without destroying the hair...
This is all just what I do and what My reactions are... Hope it helps you though..!!! 
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