Rimmer Bros have a lot of info regarding spring codes and colours on their website.....below is an extract; there is a list of colour codes, and you should be able to work out which springs are suitable if you can find the label under your rear seat squab.
''Product Description
The Spring and Damper Identification Label is located under the rear seat squab and contains identification codes (CI codes) for the springs and dampers fitted to that specific vehicle, when manufactured.''
Have a look here and scroll right down the page;
http://www.rimmerbros.co.uk/Item--i-GRID001551