You are SO up my alley with this topic!
For about the past 2 - 3 years, I've experimented with hair colors. I got the "itch" when I saw Kate Winslet with funky-colored hair in Eternal Sunshine of the Spotless Mind. So I went out and got some L'Oreal temporary hair color... I forget the exact product name, but it was a color mousse in a small can and was supposed to last 4 - 8 shampoos. I got "Chilled Plum" and LOVED it. Thus started the Funky Hair Phenomenon, which is still in progress.
My hair is currently
Midnight Blue for the underneath/bottom layer, and two tones of
Raspberry kamikaze on top. I say two tones because I bleached a section in the middle of my hair, so the Raspberry is darker on the unbleached sections and BRIGHT on the bleached sections.
I've done some myself and home and I've had applications done professionally in a salon. My hair has been black & purple, HOT pink, and various shades of maroon/red wine/sangria. I have brought pictures of Joss Stone and Pixie Acia to my stylist to use as guides for my color.
I've used (or my stylist has used) Manic Panic, Beyond the Zone, and a Paul Mitchell semi-permanent color (that was the HOT pink). Typically I find that the color gets more vibrant after the first shampoo, then fades a little each wash after that. By 4 weeks I'm noticing a "dullness" to the color; by 6 weeks I'm thinking to myself, "Yeah, I need to decide what I want to do next. Fast."
I also learned that, while the purple was probably my favorite experiment so far, it was the biggest pain in the rear. I haven't had problems with ANY of the reds or pinks rubbing off on clothing or bedding once I'm past that first night (unless I sweat/get wet - then the color drips from my wet hair). The purple bled THE WHOLE TIME it was in my hair. 4 weeks later it was still rubbing off on my pillowcase. And two issues with the fading/coloring: 1) if ANY bleached strands of hair didn't get thoroughly colored, THEY LOOKED GRAY against the properly colored hair. I did NOT spend that time and money getting my hair dyed to come out looking like I had gray hair!! 2) the purple semi-permanent colors fade to blue, and pretty fast. Purple faded much faster than any other color I used, and it didn't hold up so well once it started fading. It didn't look as "passable" for as long as the reds and pinks do, IMO. But it was a REALLY cool color and I would do it again in a heartbeat.
The reds fade to pink and you can pass them off for a couple of weeks past the end of the color's "useful life". Leave them un-touched for 8 weeks or longer, though, and the bleached sections will wind up looking brassy and orange. Not pretty.