Methods and apparatus for measuring a thickness of a coating on an object are provided. Light is directed toward the object at a predetermined location on the object such that a portion of the light interacts with the object. An image having at least two wavelength channels (e.g., color channels) is captured that is produced by the portion of the light interacting with the object. A relative shift is determined between each of the at least two wavelength channels, based on a histogram of each wavelength channel of the at least two wavelength channels. At least one of the thickness or an acceptability of the coating on the object is determined based on the determined relative shift.