This handsome fellow is the caterpillar of a white-lined sphinx moth (Hyles lineata). This caterpillar’s color can vary quite a bit. The markings on this predominantly black caterpillar can be green or orange, but the main color can be bright green or yellowish with black markings or red dots.
One consistent feature of these caterpillars is the orange horn on their back ends. This is also a good way to distinguish front and back. The horn looks like it could sting, but it can’t. It’s probably more of a visual deterrent to would-be predators.
The adult moth (below) has more uniform coloration. These moths and caterpillars are quite common but I rarely see then. This isn’t surprising considering how the adult moth blends in, but the caterpillar is quite striking and I’m surprised I haven’t seen more of them.