Multiple domains on one Drupal using URL mapping

Hello all!

I'm wondering how feasible it might be to do what I want to do.

I've got several different projects, which each have their own domain names. But there are connections between them. E.g. a page on www.blue.co.uk (made-up name for the sake of illustration) might have a topic in common with a page on www.green.co.uk.

Currently, most of it is on plain HTML. But recently I started considering using Drupal for an overhaul of one of the sites.

Then, as I've been checking out Drupal, it's occurred to me that there would be advantages to having both www.blue.co.uk and www.green.co.uk being served from one install, using some version of URL mapping. That way, they could both share some Drupal taxonomy vocabularies. Then e.g. if someone came to www.green.co.uk and found something they liked, they could click on the taxonomy tag for that topic, and the results listing would include things from the "blue" site too. That strikes me as v cool :-)

I've been searching around and reading round the subject quite a bit, and I've seen the Domain Access project,
http://drupal.org/project/domain
but not yet discovered anything exactly (reassuringly :-) ) the same as what I want to do.

Couple of specific questions:

1. Would Drupal (and mod_rewrite if appropriate) give me the control I want over the addressing?

so e.g.1
www.blue.co.uk/blue-idea/essay-about-blue/
and
www.green.co.uk/green-idea/essay-about-green/
could both be canonical addresses,

and e.g.2 (possibly more tricky)
www.blue.co.uk/shared-idea/first-essay/
and
www.green.co.uk/shared-idea/second-essay/
could both be canonical addresses?

2. Thinking about the practical structure, I have a question about which bit of the underlying Drupal site I'd be best off mapping the other sites onto (if that's how it would work).

I could imagine
www.red.co.uk/blue/
and
www.red.co.uk/green/
being used as the underlying "real" locations for blue and green, with red really where it appears to be. Would that be sensible or silly? Pros and cons? Or have I misunderstood how it would work anyway?

In general, I'm also interested in any kind of musings on "Best way to do this kind of thing if there's more than one way".

I don't have compelling reasons yet to pick Drupal 5.x or 6.x.

Thanks in advance for any clues!

Jennifer