The dyes come in all kinds of colors - from blue to purple, to green, orange and yellow.
I don't know what the practical effect of mixing them would be though. It might just turn sickly brown.
Either way mixing dyes into it wouldn't do anything, as the dye acts as a trace agent. A sample would still reveal the dyed diesel as 'red diesel'. To tell feds to 'phuck off' you'd have to remove the dye.
There's two ways - one is to add acid, which reacts with the dye and removes it from the diesel. This is what the militants do in Northern Ireland. It does, however, leave you with a corrosive fuel. :bang In theory, you should be able to thoroughly mix the fuel with water, and then use either a gravity tank or a centrifuge to get the water back out of it. But I'm not sure it's something I'd do or something that would be worth the effort..
The other is theoretical - redistilling the diesel. It would require a lot of power and so would probably not be worth the electricity costs. The dye is a much heavier fraction than diesel, so with the right temperature it should work. The right temperature is of course from 180 to 270 degrees celsius, which is a lot.. so I'm not sure I'd bother. :badidea: