I color my hair artificially all the time, and the only problems I've ever really run into were overprocessing parts of my hair and having to dye my hair brown 3 times right before my wedding because the blue green I had dyed my hair shortly before Thanksgiving had managed to leave a somewhat green tint in certain lights. My wedding was New Years Day and everything came out ok.

I haven't used the temporary dyes like that since I was younger though, but I never had problems with those washing right out.

I have had her -exact- problem. I have platinum blonde hair (bleached, of course) and I've had blue stuck in it.

From my background in cosmetology and my own personal experience, I've found that blue/green colors are the ones that tend to last the longest without fading. Red generally fades faster because the molecules don't stick to the hair as much as other colors. Green and blue are at the other end of the spectrum with explains why they might stain hair.

Hair that has been artificially lightened, or is naturally very light, is usually a lot more porous than darker, natural hair. Because of this, the hair strands tend to suck the color up and semi-permanent can become permanent.

I had my hair done with blue and pink. I put bleach over it and the pink disappeared, while the blue hung around and turned into a pool-water color. I had to dye my hair to a medium brown to take it out. The blue hasn't always stained. It does seem to rely on the quality of the dye. Now, I'm always super careful. I'm contemplating going blue again, but don't want to have to go back brown to get rid of it.

I had purple hair the first time I met both of my future in-laws. I dyed it for some random Halloween convention or something, and just happened to get a chance to meet them both while it was still bright purple. It did wash out over time, and luckily my hubbie's folks are amazing, and thought it was cute and daring. But it did take two good months to finally get all the purple out of the hair at the back of my neck.

Regards,
Jaimes

Pink likes to stay in my hair like crazy. I didn't really have problems with my blue or green cause I dyed over them but yeah.. I had pink in the ends of my blonde hair for the longest time.

My hair is red right now and it's staying pretty nicely (a natural red). After being a brunette I bleached it to a copper-y blonde and put a natural red over it. You'd think i was a natural redhead..

Also.. i want pink hair again :x

I knew a girl in high school who colored her hair blue with green leopard spots. It was pretty creative (this was also a performing arts high school, so no one was surprised by it).

The most I've done was a cranberry-grape in high school (permanent), then some purple streaks in my mid-20's (wash out type). Never had any problem with getting rid of hair color since I stick to reds and those fade rather quickly. Although once my red had been over-processed and I had 'Leeloo from 5th Element' bright orange hair. Had to end up wearing a wig in the theatre production I was in because of that (most maids in the 1940's don't have bright orange hair).