I'd say most hardcore drug users wouldn't care about the dye, but most pill abusers IMO are secretly abusing them. so unless the want to have a mouthful of blue dye and look like a smurf vampire I would think the blue dye would be a great deterrent.
It's physiological WeeZ. Abusing a drug is considered wrong doing and no body wants others to know what they did. The blue dye serve that purpose, it make you all blue so others notice you. You would think twice before you try that again lol.