Terrible Colorized $2 Bills. Suggestions?

You could just check if your bank would let you deposit them as-is.

If you paid less than face value, you might question if these items are fake. Why would the seller not deposit at a bank?

These are undoubtedly genuine - quite a few for sale on ebay.

Which would explain the half off for each note.

How easy it is to remove, depends on how it was applied -which we can't really tell. If it's some kind of indelible ink, then any solvent strong enough to remove it will likely also be strong enough to damage the underlying note.

On the other hand, if it's just a decal or sticker of some kind, it might peel right off. I once owned a very cleverly made US$1 that had been modified to have the portrait of Queen Elizabeth II instead of Washington; the portrait oval was just a sticker very lightly glued on, so you could turn it back into a normal $1 note very easily.

If it's permanent, then there is a technical issue as to it's legal tender status. Banknotes with more than 10% of their surface covered in graffiti or vandalism are deemed "unfit for reissue". Banknotes with more than 50% of their original surface damaged or otherwise obliterated are deemed "mutilated" and are no longer acceptable by banks.

It is technically a crime in the US to deliberately damage a banknote in such a way as to render it unfit for reissue; there is no exemption given for artwork (which may be why my monarchistic $1 note was not permanently altered). But it's not a crime to try to spend a note that has been damaged in that way.