I would say those are all legit, actually. The colored one is from some drawings he did for Hollywood. We have the other one - two actors fighting - and in a handwritten note to Martin that we got with the drawing, he mentions that out of the two drawings he was enclosing, this one of the woman walking the dogs is the one he prefers.
The sketches all flow, I don't see any hesitation in the lines, and there are a lot of typical Bukowski touches in them. That signature on the color drawing is shaky, but the "Ch" is correct. In the second one the hair is typical Bukowski, and in the third one, the sun and the bird are his style. It would be difficult to fake those. I know they just look like blobs sometimes, but you can definitely see consistent shapes in his sketches, and I think these pass the test. To me, anyway. Put it this way; if they were offered to me for sale I would buy them.