You will find a similar thread under 'Commando Street Scrambler Questions'.
The SS came only in yellow and orange. Anything else is an owner's choice - not original.
And, both the yellow and the orange were very specific colors - I think they're called Norton Yellow and Norton Orange (really original).
Seriously, they are unique and easy to spot when sitting beside a non-Norton color.
The side covers were always black.
The SS came with a sidestand stock. Having said that, the '71 sidestand was a bit of a standing (pardon the pun) joke since it refused to stay attached to the bike. The stand itself had a pivot hole that fitted over a 1/2" pin welded to the underside. It was held in place on the pin by an external C-Clip. The groove for the C-clip was extremely shallow and there was no washer or bushing of any sort to give it strength. Consequently, in a few miles, occasionally on the way home from the dealer, the weight of the sidestand would overcome the C-Clip which would pop out of the shallow groove and the stand would fall off. On later Commandos, '72 and on, the sidestand was attached with a bolt that went though the pivot hole in the sidestand and bolted to a flange on the frame with a securing nut and washer.
If you have a '71 frame with no pin for a sidestand, it's been removed - not uncommon.
To keep my '71 SS original AND keep the stand in place, I put a deeper groove in the pin about 1/2 way up and then drilled and tapped a small hole in the back of the stand pivot to hold a dogleg bolt. After installation I filled the hole and painted over it. The mod cannot be seen and the stand is on for good.
I have 3 1971 SS frames and can find no indication of "additional side plates to keep debris out".
I think the plates you refer to were braces on the lower frame tubes to strengthen them at the engine mounts and these existed on all '71 models.
I do love the way you call the skid plate a "bash" plate. Just like a real Brit! And probably more accurate too!!