If u put food colouring in a potato seed will the potato grow purple?

that would be awesome

no it might turn blue u didnt say purple food die so it might be roze of green i think u know what i mean

No, if you're only working with the seeds u would have to change the potatoes' genes.
But u might get some effect if u constantly water the plant with heavily dyed water.(or u can door potatos that are already purple)