Hi Rich and thanks for your wonderful picture of a Sphinx Moth larvae. There are two species, Proserpinus lucidus and Proserpinus clarkiae. From the pictures I can find, it is more likely to be the first, called a Bear Sphinx Moth and the color matches the L5 form. The moth is a beautiful greenish color and the larvae lives on plants in the Evening Primrose family, Onagraceae.
In short, a wonderful find and thanks so much for sharing it!

https://www.sphingidae.us/proserpinus-lucidus.html

Thanks you so much.