Not all grubs are white.
"Grub" is a term for a specific phase of life (egg, larvae, grub, etc.) which a multitude of insects all go through.
That's an excellent pic and I am going to throw out "cabbage worm," based on your photo ...
I'd think it was a butterfly caterpillar UNLESS you dug it out of the soil ... if you found it above ground then, I'm going with butterfly caterpillar ...
Anyone else?