Hi, I am trying to find a paint that would be a good match for a 1971 XKE silver gray 3308
Thank you.

 

Here is one cross reference.

Jaguar Paint Codes

 

In my experience, older paint codes are rarely available. I've used three ways to select color for restoration projects....
1. Remove a part from the car that is the original color. Preferably a part that has been protected from fading or chemical exposure. Take the part to an automotive paint supplier and ask them to match. In my opinion this is the most accurate way to get a modern paint to correlate with an older color.
2. If #1 isn't possible, try to find a modern car (newer than 2010) that has a color you consider close to the original paint. I've tried this by comparing color chips online at paintref.com and ppgpaintit.com. I've also done this by just looking at cars. Then ask your paint supplier to mix a sample of the modern code from those references. You may have to try several samples to get a code you consider acceptable.
3. In some rare cases, I've found older paint codes have been re-created in modern paint formulas. In my experience, Glasurit and PPG have a limited database specifically for cross reference to older codes. Ask your paint supplier to contact the paint company HQ to see if there is anything available.

cheers, Richard