I would expect the areas on its lower sides that are sort of cream colored to be more yellow if it were a pastel, but some pastels don't hold their color at all well.

Another question to ask is, even if it is a pastel, do you have any interest in owning that snake? I'd say no. You can get reasonable quality male pastels for around $100 or even less if you shop around. If it were a female, that would be different, because an extra female pastel is a good thing, even if she isn't the best pastel, but I wouldn't want such a browned out male pastel.