According to the Service Manual for 2010-11 XF cars the coil springs are color coded for identification purposes since different models use different spring rates. My car was not sitting level, the ride height on one corner was low by about 10mm. This is within the the tolerance given in the Service Manual but is visible to the naked eye.
Anyway thinking that it might be problem with the spring or the mounting I pulled the spring/shock assembly to take a look. This was when I discovered the color coding on the spring.
I have attached pictures of the color coding on the front springs-----the color coding is different and I suspect that someone has installed the wrong spring. Both rear springs have the same color coding------blue/blue/white rings on top and single orange on the bottom.

Does anyone have a key for the color coding?

red/red/green on top, orange on bottom

red/red/green on top, white on bottom

 

I have exactly the same spring Red,Red,Blue with an Orange band below. I have a Jaguar XF Premium Luxury 2993cc 177kw 241HP with 355mm front discs. After a bit of reading, the top 3 colours specify the actual spring specification spring rate, free length, compressed length, number of coils, diameters etc. Different XF models have different springs depending on the weight and performance of the car. However there is a natural manufacturing variation, so although the springs with that colour code are within specification, there will be a slightly variation in length when the spring is compressed by the weight at that corner of the car which would be seen as a slight difference in ride height at that wheels. So the manufacturer splits this acceptable ride height at a specific weight into several narrower height tolerance bands (grading, matching or selective assembly) and gives each spring the single colour code to indicate the more specific part of the acceptable tolerance band that the spring lies in. This then allows the assembly factory to pick two springs within the same narrower tolerance band so that the ride height left and right are as similar as possible. The Jaguar XF front shock absorber seems to be the same for the cars without smart variable suspension systems, only the spring varies.
The main source I used was https://pmmonline.co.uk/technical/wh...-road-springs/
I suspect that replacement springs are not graded as this would entail more part numbers but are [may be] matched when supplied in pairs and possibly one of the reasons to replace both at the same time. I have found an exact 4 colour code match on a scrap car so I will only replace the shock/spring assembly on the side with the broken spring. I don't want to be faced with the question as to whether the end break I have is acceptable within the new MoT guidance.