Manic Panic hairdyes are fantastic for bright colours, but relatively expensive. I think they're about 11-12 quid a go.
Directions hair dyes are pretty good, chemical free and less expensive. I think they're about 5 quid.
You can find these on t'internet or, if you live near a Blue Banana, in there.
Personally., I'd reccomend the Directions seeing as it's chemical free and so conditioning.
Small tip: Because the top of your hair is black, the colour won't cover it, so when you've finished dying your hair, but a small amount of the dye in your conditioner. When you're washing your hair, leave the conditioner in for about 5 minutes, and this should keep it fresh!
I used to have neon turquiose hair. And pink. And blue. And any other colour possible, and the Directions dye was the best reasonably priced dye I found.
And none of it is "normal" colours
I used to constantly dye mine and ruined my hair - its still not very good now and i've not put dye on it for nearly 3 years.
I have use all sorts, sometimes it lasted a fortnight other times only a few days before it faded completely.
I wish I could remember the name of the last product I used - it was by far the best one for lasting. I picked it up in superdrug mainly then noticed asda stocked it for a short period of time. I'm sure it was mainly a streaking kit but it was pretty awesome. I had a look online for it but cannot find it - it came with a bottle of peroxide/mixing bowl/streaking cap/ a packet of red powdered bleach/ application brush and one of the little hooks you get for pulling hair through the caps. My description might make someone else remember the name of it.
It was a very strong dye, it is basically powdered colour bleach, it did fade in time. I used the red one mainly.
I also used this - which did fade but I had a nice tub of it which I just opened up again and slopped more on my head. http://www.glitterstore.co.uk/index.php/catalog/product/view/id/1327/?utm_source=googlebase&utm_medium=organic&utm_campaign=base
I know this is an old thread but I have been dying the side of my hair bright colours for a few years now, the best hair dye I have found is Special Effects which you can buy on beeunique.com. It costs about £10 with a couple of quid postage but it lasts around 2 months at a time and fades really nicely - you get about 2 or 3 different colours as it fades. I have used Cherry Bomb (red/pink/glows under uv) and Blue Mayhem (purple/blue) and I can safely say they are my favourite dyes. Directions is pretty good but it depends on what colour you get really, and after a while you end up having to redye it every week which is annoying. To keep your hair in good condition all you have to do is make sure you use deep conditioner often basically! My hair is still in good condition
I've been using directions oranges and reds for a few months now. I've also used the pinks and purples in the past. I can make them last for about 2 weeks and they are amazing colours that condition your hair. My hair is light blonde underneath though. Putting some in your conditioner is a good tip too.
Even though its not permanent when you want to go back to a normal colour you can just let it fade out which is what i'm doing now
For red hair Henna is good but its vibrancy depends on the natural colour of your hair. Henna is permanent though, and the more you use it the richer the colour is. Not to mention its incredibly good for the health of your hair. It's just less predictable how it'll come out...