These are the standard knobs used for certain on the K1 and K3 Soundcraft desks and probably a few others, not all of these desks used these colours and/or Dual knobs but I have listed what I have seen in the arrangements I have seen them.
First size 14.85 mm high 11.00 mm wide at widest point on the single knob, the double knob is a single on top off a base size 14.11 mm high14.20 wide, all widths measured at the widest points.
I have a second larger single knob which is 17.41mm high 13.87mm wide
These knobs are a two shot mould so are the base units which also have a colour in them to match the tops, some colours were only used on one model of mixer.
Single S1292 Grey, S1290 Yellow , S1291 Aqua, Red S2077, Blue S2078, Black