Mitomycin-C is a purple-coloured solution that can destroy cells. It attacks cancerous cells when put into the bladder but does little damage to your normal, healthy bladder lining. It is a chemotherapy drug, but because it is put straight into your bladder and not injected into your veins, you will not get the side effects people often associate with chemotherapy, such as hair loss, nausea and vomiting.
(Above Reference taken from Guys and St Thomas Hospital patient information sheet.)
So you should be ok to dye your hair during treatment. Do take advice from your hairdresser.
