FAR 45.23, 25, 27 & 29 seem to cover all aspects of size and location of marks, etc.

But I can't find any reference requiring a particular color contrast between the airframe color and the mark color. Do the N Numbers need to be visible/distinguishable from a certain minimum distance? Black marks on a white airframe might be most visible from a distance compared to light cream colored marks on a white airframe.

I plan to have pretty basic contrasting N Numbers on 4ZQ for the inspection but what about down the road when I get a bit more creative? I wonder if any color combinations have actually been rejected by FAA.

Angier Ames
N4ZQ