Good job finding the correct tint for the IC orange color! That has always plagued my repaints in the past, either too orange or too red. One thing I should bring to your attention, though, is that the logo on the front does not correctly match the name...
The logo you have on the nose is called the "split-rail" logo and was in use from 1968-1972 under the "new" IC image.

By close inspection of the logo, one can see that by splitting the rail in half and offsetting the dot above, the logo effectively says "IC".
The logo changed after the "Gulf" was added to the end of the name. The rail was fused back together and the dot was centered during the three ICG paint-schemes.

In addition to the logo change, the orange paint on the long hood came up higher on the ICG units than the original IC paintjob. I always figured that the separating line was even with the handrails on an IC unit, and about a foot above them for the ICG units. This may not have been standard, but I've seen this enough to notice it.
I don't recall any of the GP9s to have been painted in the 1979 orange and grey, or the short-lived orange "pumpkin" schemes.
Regardless, I think the repaint is great and the number fonts look correct, which I have also found to be challenging!