So now that you're all happily colored, with the proper care you should expect your color to stay its brightest for three to four weeks, and to be considerably faded after six to eight weeks. If you're using permanent or semi-permanent dye, and it's been completely washed out, it shouldn't rub off even on white.

As a minimum, use shampoo and conditioner formulated for color-treated hair. This won't remove the dye as much as normal stuff and it has extra protection from outside damage. Do not use anything with alcohol in it! Check the label to make sure. Most pomade and mousse is fine, but a lot of cheap gel has alcohol. Try not to wash your hair every day; go for every three days or so, and use a shower cap in between. If your hair ever gets especially dirty, I notice that more dye tends to come off. Limit long exposure to sun; it's both damaging and color-removing.

Unless you're aiming for white, avoid bleaching the same hair twice. Bleach already does a fair amount of damage, it doesn't pay to have the hair go through it unnecessarily. However, bleach will take out any pre-existing dye just as it does your natural color. i.e., if you have burgundy hair and bleach it, it'll end up blond, not pink. Light dye isn't an alternative; it has very minimal lightening power if any.

Trying to bleach dyed black hair WILL kill it. Do so at your own risk. Not only will it be dead, it doesn't work very well and the lightest your hair will usually get is a copper color.

You'll notice when you're fading. The color will be duller, or a completely different color (if you put in blue dye, it fades to a turquoise green), and your underlying bleached hair or your natural color will start to show. Even if it sill looks mostly good, it's probably a lot duller than it was if it's been a few weeks. Bangs and ends fade much quicker. I like to do a full head redo every two months at least. You want to saturate all the hair again, even if it's not completely faded. Go through the same process as the first time (wash conditioner, heat, color, bag, waiting, heat, remove bag, more heat).

I often do touch-ups on spots that fade especially quickly by just putting dye directly on hair that's fairly clean, but will be washed within a day. Basically, I just put the dye in and go walking around normally, making sure I don't rub it on anything, and then wash at the end of the day. It's not the most effective way of setting, but it's a quick way to get rid of annoying blonde patches. I'm pretty sure I get blonde spots on my upper hairline because I use Proactiv face wash, which has benzonyl peroxide and can seep into the hairline when I wash my face. I don't know if any other face products contain peroxide, but it doesn't hurt to check. If so, take some care not to get the product on your hair.

Dyeing over in a different color depends on the colors being used. Very dark colors don't completely fade, and putting any color over them is going to end up as a very dark combination of the colors.