Hi Michael,

> I'm not quite following how that actually works
> - for instance what do the layers assignment do
> to the category? I mean do the layers have an
> on/off state that controls the category being
> on/off,

The category becomes the parent to the layers, where you can control on/off of individual layers or turn on/off the category which contains those layers.

> and does the color of the layers control
> the colors of the category?

Colors don't come under any of them, that's controlled separately with a combination of 'object preferences', 'edit object display' the filtering system and hide/show.

If you need more info I'll be glad to show you pictorially to explain it once I get home.

Cheers