Hp color laser jet printer cm1312nfi mfp is bleeding magenta?

It could be due to several reasons. Most common reason could be the print cartridge. How long you have been using it? and what is the toner percentage? I recommend to take the magenta cartridge out of the device and have a general look at it, this problem usually needs a professional assist to be solved. If your printer is still under warranty I recommend to contact HP fr service and support.