As mentioned above the Blue colors were Viking and Guardsman Blue
The 142 car at Whitby was seriously researched by John Knight one of our local experts, and he had the paint mixed by one of the old timers ..
Portofino was a 60’s and 70’s color and is a close fit to the blues used. Mine is a match to the Superformance color , and the code comes from Todd Buttrick. The actual mix that Superformance uses is now known…to a few select experts.
Another close match is the color of the Whitby coupe – I think Atlantic blue -Jeff can help us here. Two other members have found great light blues, like Brittany Blue (3 or 4 cars), another was from a Porche – Ed Hubbard can help here
AS for original colors, as already said the race cars really were just painted with what was available, the street cars had color palettes that owners could choose from, some were pre painted prior to being shipped from UK, but so many times the shippers banged them up that they were repainted locally . The Rinsey Mills book lists each CSX number and the paint color it left the factory, Red White Black and Green feature a lot.
The team stripes (on fender) were just rattle can paint often on the day of the race to differentiate the drivers, as all the team cars were same color.
CSX2000 was painted diff colors to make it seem as if they had many cars. Yes it was Yellow for the NY show, but before and immediately after that it was a different color (I forget which).
Decals as CHEPSK8 says were just placed on the cars, I have literally hundreds of race photos across 8 books and each time they are just on cars, even two team cars in same race might NOT be same.
If you want to emulate a race car, then choose one race and driver. Mine is of Ken Miles car at I think Sebring in 1965. Only the number 73 is my own, and I don’t have a Dunlop decal.
Don’t have my books as I’m in a Hotel room , or I could give you a reference page