is it possible to alter your natural hair colour with nanotechnology or biotechnology? I've heard they've performed it on mice, so will it be possible for humans, if so, when?

I may not be seeing the research you're referring to, but it looks like in mice the only hair color changes I've seen have been returning from albino to a colour, rather than changing from one colour to another. (It may be possible to define hair colour before birth, but I haven't seen it during the animal's life).

So...  could be some time before we see it on the pharmacy shelves!

This is only possible in mice using transgenic technology to modify the relevant gene(s) in the germline which therefore affects the whole animal. The equivalent technology in man is not worked up at all and is illegal in all developed countries. The ethics of this are very dubious to put it mildly!