I've been using Directions
since the early 90's. It used to be the only sort i could get, then i did try other types when they came out, but i wasn't ever that impressed.
I agree that blue washes out easiest, (need to redo mine tomorrow!) and red stays in longest (or at least fades to the prettiest colours).
The way i do it is:
Bleach hair until white/yellow/as light as i can go before it drops off.
Shampoo out the bleach, noting that my hair is now all slithery and feels like slime...mmm healthy.
Towel dry hair and comb through (carefully so you don't snap it all off!)
Apply dye to hair/ears/sink/dressing gown/shower curtain etc
Comb hair back in cool John Travolta style
Sit and watch TV/lurk on Craftster until the wee small hours
Rinse hair until water is almost clear, or until your arm hurts or until you get bored.
Towel dry using old dyeing towel, put on 3rd best pyjamas and go to bed.
wake up and see your pillow now matches your hair, so does your bath, and the floor.
You shouldn't need to put more colour on for a couple of weeks, or just let it fade out like a My Little Pony, and see how long you can go before re-bleaching your roots.
I have never managed to keep a colour in my hair any longer than about 2 weeks, even without washing it. I don't think it would work on unbleached hair unless it was really naturally blonde, but i hear it works really well on grey hair!
I would love to try some of these wonderful American brands and see if they stay in for longer. Merricat17 thanks for that link, they deliver internationally!