When we first meet Colbrand, he's assisting Mr. B in keeping Pamela prisoner. So, naturally, he's not Pamela's favorite person, and her disdain is really clear in her first description of him:
He is a Giant of a Man, for Stature . . . and large-bon'd, and scraggy; and a Hand!—I never saw such an one in my Life. He has great staring Eyes, like the bull's that frighten'd me so. Vast Jaw-bones sticking out; Eyebrows hanging over his Eyes; two great Scars upon his Forehead, and one on his left Cheek; and two huge Whiskers, and a monstrous wide Mouth; blubber Lips, long yellow Teeth, and a hideous Grin. He wears his own frightful long Hair, ty'd up in a great black Bag; a black Crape Neckcloth, about a long ugly Neck; and his Throat sticking out like a Wen. As to the rest, he was drest well enough, and had a Sword on, with a nasty red Knot to it; Leather Garters, buckled below his Knees; and a Foot—near as long as my Arm, I verily think. (53.19)
Kind of sounds like a cross between Frankenstein's monster and Dracula, no? Ultimately, though, Colbrand reveals himself as kind and devoted to Pamela's safety, so she comes to value him greatly. He's especially useful when Pamela is trying to escape Lady Davers—he helps fend off Lady D's servants while Pamela makes a run for it.
The contrast between Colbrand's hideous exterior and his not-so-bad interior is a nice corrective to Mrs. Jewkes. It definitely raises some questions for us: is Colbrand allowed to be ugly and kind because he's a dude? Or is this a little moment of Richardson telling us not to trust appearances, after all?