Is it possible to dye my (dyed)red hair into green?

Yes and No....In the hair color world red and green are opposites (they cancel eachother out) It is possible to bleach red hair to blonde, but you would have to be really careful not to damage the hair, if you could get enough of the red out, then you could put green...you might do better to bleach most of the red out, put an Ash toned blonde on it, then do the green. But you would be very brave to do that yourself...I would go to a proffessional if you really want it.