Bathymetric maps often use false colors to illustrate different aquatic depths.
Idioms and Phrases with false colors
Pretense, misrepresentation, or hypocrisy; deceptive statements or actions. For example, She's sailing under false colors—she claims to be a Republican, but endorses Democratic legislation. This term alludes to the practice of pirate ships
sailing under false colors—that is, running a particular flag specifically to lure another vessel close enough to be captured.
[ Late 1600s