Hey Raf......your reaching out to a point that favours the individual taste .......however on the subject you ve raised here s my 2 cents worth.
Re the engine....you presently have what seems to be gloss black ........general consensus and keeping original as you ve mentioned in previous posts regarding the restoration.......this should be "Satin Black". It is a product you can pick up in a spray can under the brand name "VHT".
It s a long lasting job if the surface is properly cleaned and prepared and is cheaper and easier to touch up if need be than the 2 pac option.
On the subject of the tank, side covers etc.......nothing else other than "Macho Maroon"...........it ain t called that for nothing .
Matched with the gold and black decals.
Your bike , presently , in the photos you ve shown ...seems to be a few shades darker than the original "Macho " scheme .
There aren t any paint codes available for any schemes present "in the day" as they were nt being used back then.
Any reference to an original colour would have to be done via paint matching from an original NOS part .
Your own choice will be the best one........as that's what matters.