Colour codes on Ford springs

[Bobberoo99]

Hi, can anyone explain what the colour codes are for on the springs on my Focus? I can't seem to find them on the springs on the car which creates my first problem as I think I may replace them when I do a suspension bush overhaul on the rear of the car this year, when I had a quick look on the weekend I couldn't see the colour codes but as I say it was just a quick look and the springs are starting to flake the plasic coating off, my thought is as i'll be taking them off the car to replace all the bushes and they're flaking anyway why not replace them? Unless people have other suggestions that is? I can find plenty of springs on eBay including genuine Ford ones but there's a huge price difference when it comes to the colour codes, so any help in finding out which ones I need and explaining the difference would be greatly appreciated!!