Pink and reds fade the fastest...someone told me that it was because the molecule is larger...w/e...logistically, I don't see how molecular size can make THAT big of difference.
However, to make your hair dye last longer:
- shampoo every other day, condition daily
- if you can, shower every other day
- use cool water to wash your hair (quickly shampoo your hair in cold water, rinse and then put in the conditioner, crank up the water temp to wash your body, then turn it super cool to rinse the conditioner)
- don't rub your hair with a towel, instead get a towel-turban or blot your hair
- don't blow dry daily
- use shampoo for colored or treated hair
- keep your hair moisturized...get a leave in conditioner
- don't straighten daily
Hopefully these help out! I've been dying my hair for a long time. I don't see how adding dye to the conditioner would be a good idea, especially since dye is damaging and needs to be in your hair for a long time..plus the ingredients in conditioner might block the color or mess with the color.