I think (with little to no expertise in this) that you are correct in your ID of Western or Green Whip Snake (Hierophis viridiflavus).
I find snakes difficult as there is so much variation in the patterns of the scales. In the case of the green whip snake, these can be anything from almost no pattern, just blackish to vivid yellow/white blotches/bars.
However, a search of iNaturalist seems to confirm the ID, with a very similar photo, as well as several more that point in the same direction. Many of the photos show the same whitish ring around the top of the head and a gradation of patterns from the head along the body.