In the more recent design standards, knob shape and relative position in the cockpit are prescribed. For an airplane approved and designed in recent years, there will be an excellent control knob, motion and location layout. For older airplanes, or somewhat newer planes still made to a very old design, the knob shape and relative position may not be as we expect from a newer airplane.
I was test flying a deHaviiland Beaver a week ago. It has the original throttle control (the prop and mixture have been removed). The original DHC throttle knob is black (correct) and exactly the shape a landing gear knob should be (not ideal). As a wheel plane, not a big deal, but the airplane will be put on amphibian floats this spring - and I know that the knob shape for the landing gear for those floats is more like a throttle knob shape than a wheel shape! Amphibian airplanes have additional landing gear selection disciplines, so I'm not really worried about this, but it's noteworthy. In the mean time, when engine controls are being changed as a part of a deign change, I will not approve them unless they are compliant with the latest design requirements, regardless of the airplane's certification basis - just to harmonize an older plane with the new requirements.
the regulators and airplane builders do their best to reduce human factors risks in the cockpit, but the pilot still has some responsibility for Select/Identify/Confirm/Move/Check for intended outcome......