Here's my two cents worth on texture and painting.

The legs and arms are a faded black or charcoal gray color. The lighting used during filming greatly affected how they appeared on TV. Sometimes the legs looked shiny, other times they didn't. Sometimes they looked silver. I know a light diffuser will make the light off the rubber appear to have a silver sheen, but sometimes I think they really were painted with a silver hue in several episodes. After 40 years I've never been able to pinpoint it. However I think they are anything but glossy black.

The torso had a definite texture. I noticed this even watching the show in the 60s on a 1947 Dumont black & white TV. It was definitely a dull silver or light gray during the first season. They brightened it up a bit for the 2nd and 3rd seasons, but it was never a reflective chrome silver.
That would never have worked well with studio lighting. As it was they often sprayed the robot's bubble (as well as the astrogator) with dullcoat to cut down the glare.

The wheels are a chrome metallic silver.

I painted the "rubber" parts on my B9 a dark, very semi-gloss charcoal gray using latex paint. I felt this was a good idea because latex will stretch or shrink and not crack like enamel. I mixed flat black with a bit of semi-gloss white. I applied it with a foam brush, giving it two coats.

The tread belts are black. I left them the natural black color of the pipe tape but painting them with a flat black or that Plasti Dip stuff isn't a bad idea.

For the torso I first sprayed the whole thing with a gray primer. After that I hit it with a coat of the fleck stone stuff. I let it dry for a day then lightly sanded off the high spots. Then I covered it with a basic generic silver spray paint. Once dry I sprayed the whole thing with some Krylon matte finish. The result makes it look like cast aluminum.

The hammered finish works really well. Several people have looked at my B9 up close and asked how I formed the metal parts. There is no metal on my robot at all with the exception of the metal axles holding the wheels and the bezel around the chest buttons. The lower parts (plates and knee hinges and starburst pattern tread section covers) have the hammered finish. I also used it on the waist plate. The tread section is textured and painted silver and sprayed with matte finish like the torso.

The bottom line is that you can paint it any way you desire. This is just what I thought worked best. It's what I personally see from the set photos and viewing the episodes.

I recently acquired the Lost In Space View Master reel packet. There are several 3-D shots of the robot with very good lighting. It really gives you an idea of what the color was probably like, moreso than watching the episodes or seeing the faded photos.
The legs definitely look like radiator hose black to me. You be the judge. Two frames from the View master are below.