69XR7 posted a reply in the Parts forum that addresses the color differences. I have attached a screen shot or you can cruise through the Parts Forum - I found it in the "Marketplace - 69-70 Parts for Sale - Parts is Parts" postings.
Registered: May 2001
This is an email i recieved from a person i think is knowledgable about cougars...........
"the dash clusters are different in a few ways. The most important to note is the Cougar reg dash will not interchange with the XR7 dash w/tach unless the whole frt wire harness and interior harness are swapped in as well.A fire will be the result of any incompatibilities.Also note that there is an early and a late 69 that carries thru 70.On the back of the cluster there is either a blue or red plastic film. Again Fire will be the result if you mix em up Careful here Thought you should know. Also 69 XR7 is diff than 70 XR7 and different again for Cougar 69 or 70 when it comes to the wiring harness' you must have all the compatible parts"