These are both beautifully done, Rich! I'm very familiar with that silver gray Mungyo, and it's fascinating to think of using that for a bright sky. I am thinking your ref photos might have had very bright, or even washed out skies - a common problem with digital photography. This approach can make the painting true to the ref photo while still giving color and a sense of depth to a flat sky. Very inspired choice!
Nice to read you are still using the Nupastels for your base layer. I think they are a great way to build color but saves on OP's!