Don;

Non-critical differences to the basic function, like centrifugal advance curve, vacuum retard/advance notwithstanding, all B18 and even B20 distributors fit and are interchangeable.

I'd put the engine to Ignition point of #1 before removing the old one (and make note of the dist drive key when removing it), just as a reference point for fitting the new one, and since I'd be static timing once the new one was in place, I'd be immediately ready for that step.

Suggested reading: http://www.sw-em.com/Volvo%20Ignition%20from%20Scratch.htm

As far as asking about wires by their color...it's better to refer to them by their terminations...that way there can be no mistake...

Cheers!