As far as I know, strawberry, blueberry, fruit loop etc tetras are all injected with dyes. They are usually the albino form of the blackskirt tetra. This could be in our new Characin forum, btw.
Yes and the dyed process is cruel and they shouldn't be bought.
One such way to dye them is to dip them in acid to remove their slime coat. Dyed fish will lose their color after a few weeks or a couple months and you'll end up with what the fish really looks like anyways.
Do not buy dyed fish or they'll keep making them as long as theirs a demand on them.