Oh right. Yes, I'm aware of the problem of bits disappearing - I
might have to use a different colour - had a look at Stingray, and
it has bluey/tourqoisey bits. Perhaps a custom panel done in Cadmium
Yellow (which looks orange, and is very opaque) would be a better
idea...

It would be a bad idea, TBH.

Blue was used because (on film) it was furthest on the spectrum from
any of the colours in skin tones. Green has been brought in too, so
that actors can wear jeans without them disappearing.

But..., Stingray doesn't have fleshtones. It's a whitish submarine with
bluey bits. There is a Troy Tempest figure, but he's very small, and
rather
hard to see through the little windows. If the most effective isolation is
to be had by using a background which is the complement of the thing we
want
to isolate, then an orangey colour against blue is about as good as it
gets.

True enough. I was really going for the question a couple of posts ago where
you were asking "Why blue/green?"

If you can make a good enough backdrop (i.e. where the entire background has
the same pixel colour value), any colour will do, as long as there are no
foreground objects which will map to the same colour. In reality, this is
quite difficult, though. For my next project, I'm planning to "hand paint"
(rotoscope) my mattes or buy something to use outside MSP, such as
Chrominator.