Yay, the knobs I ordered came in!
These are two different styles of knobs, both originally designed by a company called Davies Molding back in the '50s or '60s, and which have been very popular on radios, amplifiers, and audio effects evr since. (Since all the design patents have long since expired, they're made by a number of different manufacturers now; I'm not entirely clear on where mine are sourced.) The narrower style, with the rounded top, white line pointer, and fluted sides, is called the 1900H; the one with the ridged sides and extended pointer is the 1400. I ordered a bunch of the 1900H in each of black, white, and red, and several of the 1400 in black. (The colored 1900Hes weren't available with the more reliable brass inserts, but do still have a set screw to hold them onto a smooth-shafted potentiometer.)
Eurorack module design is a bit eclectic at the best of times, and my melange of homebrew and homebuilt modules is far from the most unified system out there. But I think the matching knobs serve to pull the system together somewhat, while still giving things a bit of contrast. The VCF is the big example there — the knobs that affect the frequency are both white, the ones that affect the Q (resonance) are black, and the input volume is a contrasting red.
