Can I color dark, thick hair into rainbow shades without bleaching?

I haven't bleached my hair (ever), and I was wondering-- is there a way to get an unnatural hair color (like the blues, greens, pinks, etc) without bleaching? I have dark, thick hair, which is a huge problem with coloring unnaturally. Demi-permanent hair dye just doesn't come in sherbet, does it? Now, I have heard of henna, which doesn't come out unless you wash it with mineral oil, and comes in black, red, and brown.

Does it come in any pastels?!

Thanks for all your help, Answerers!

Can I color dark, thick hair into rainbow shades without bleaching?

you have to bleach it my dear, but you must be careful because you don't want to fry it out. Use a 30-40 developer. Good luck.

Can I color dark, thick hair into rainbow shades without bleaching?

rainbow hair? ew ew ew