There are painted on the actual springs. They're about the same size as a 20p coin.
For the front, try looking up into the arch above the wheel. As for the rear, I could only see them by looking under the bumper at the back.
The ones on my PD130 are yellow and purple, where as the ones on my 1.8T are white and blue.
Sorry to be a pain in the arse, I just want it to handle better...