Really stupid question about hair colour ...

[NotQuiteCockney]

I am debating messing with mine ... I would like to have patches of blue or red or purple or green or something.

To do this, do I have to bleach my hair first? Presumably if I'm only monkeying with the ends, the risk of damage to the roots is zero?

My hair is pretty damn short, but if I don't like the results, I can just cut it off again, right?

And is this something I can do at home? Or do I have to deal with hairdressers?

You use dot be able to get small pots of "extreme" colours whic ,eant you didn't need to bleach it. I don't know if the still do them now htough.
Don't see why you can't do it at home.

What colour is your hair naturally? It it's anything other than blonde you may find you just turn orange and the colour doesn't 'take' in which case you'd be better off at the hairdressers - find a hairdressing college, they'll do it for free or very cheap because they love getting a chance to do colours.

If you want really traffic stopping colour, then I would recommend bleaching first.
Otherwise just use shades that will stand out on your hair colour.
You can do it at home with an old dish/plate to put the dye on and a Hair dye brush if you can find one.
I had one fom the Body shop years ago. Much better for precision dyeing!

Oh, whoops, should have said. My hair is nearly black, with some grey patches (which I don't want to get rid of).

It's not the cost, I just don't like going to hairdressers. I cut my own hair.

Every so often, I get patterns shaved into my head, which I do have to go get done ...

Any 'alternative' shop or market stall should do the pots. Our local does.
Here's the brush I was talking about.

Do these colours last long? I think I'd be ok with them being temporary.

(My actual plan is to try to dye the bits that stick up after I've worn my bike helmet. Given I wear my bike helmet every bloody day, so spiked-by-bike-helmet is my normal hairstyle, I think I should dye it to work with that style. )

They last as long as any other semi-permenant dye unless you bleach before, then they may last a bit longer!
I used to do mine a lot before ds! I really need to do it again. I may go for blue streaks!

You will deffo need to bleach first then. Purple tips would probably take quite easily though.

Try looking out for these dyes But you do need to bleach (technically called 'lifting' first).

I don't know how long semi-permanent dyes last, I've never dyed my hair at all. (Ok, I used a purple wash when I was in high school, but it did nothing. Oh, and I used to use henna, but it started turning my grey patches into red patches ...)

Is it difficult to just bleach (lift, whatever) a bit of my hair? I don't want to go blonde, and I'm nervous about getting any chemicals on my scalp. (My mom had female-pattern baldness or whatever you call it. I appear not to be getting this, but still ...)

Not at all Put some vaseline on the bits you don't want to get - don't worry it shampoos out fine - also some round your hairline to protect from splatters. Use a Q-tip or similar to paint it on.

Ok, this gives me lots to think about.

I'm massively sleep-deprived at the moment and thoroughly insane, but may well have a fiddle with this sometime soon.

Semi- permanent means for six weeks or so they are vibrant but they fade and permanently remain. In my hair semi-permanent means they change the colour for a week and then wreck my hair till I get that bit cut off

NB buy some Vosene shampoo, if it goes wrong, this will remove the majority of the colour a lot quicker than growing it out.

Tomato ketchup for toning down any brassy blonde bits after the bleach too.

Oh, if it goes wrong, I'll just shave my head. I do that every few months anyway. I'm worried about damaging my roots, but not my hair - hair is disposable.

Semi-permenant usually last for about 6 weeks depending on how often you wash your hair.
With nearly black hair, I would really recommend lifting/bleaching. Shouldn't be too hard with the brush I linked to.

Yes, it does sound like lifting/bleaching is going to be necessary. I guess I could try dyeing it without lifting, and see how I like it, but I really want shocking strong colour, not subtle stuff.

Presumably dyeing, lifting and redying could produce strange results?

Depends how you feel about being a ginger

I have nothing against red hair, but it's not what I'm actually trying for here.

whistles nonchalantly

Sorry, didn't realise there was a link there, thought it was some ginger-related thing, rather than a paging-me thing.