www.jec.org.uk

A small step in the right direction. I got my calipers vapour blasted a few days ago, but only as I wanted to get a pair off one of the other cars done.

Initially I was extremely pleased with the results. However, vapour blasting consists of blasting very fine sand within a water stream and I spent longer cleaning out the grains of residual sand than the guy took to clean the calipers. The results speak for themselves: before and after:
Can anyone offer any advice on what colour the calipers would have been when new. I'm guessing silver or gold.

Is there a better means to clean calipers?

I think the XJS predated the trend for painted calipers. When I last bought some (for an XJ6, but I think they're the same), they were yellowish, which I think is an anticorrosion layer of zinc, cadmium or something else, but it was very thin and they soon turned rusty.
When I overhauled those on my XJS, I sprayed them with Halfords' red brake paint, as it approximated to the bodyshell colour, and made tbe brakes look "cool" through the holes in the pepperpot wheels.