Hi Sherrel! Well, seeing as the GP15 is a Frisco prototype... then I would be inclined to believe it to be the correct color? (Just being a smart azz! )
Let's see. Two parts of too Red and two parts of too Orange should do it. We should now have Frisco RORANGE!
If you can find it, Floquil Daylight Red is a pretty close match for Frisco orange (plus, you don't have to mix anything). Alternatively, I have heard that Chevrolet used the same paint for its engines ("Chevy orange). GS