Methods and apparatus to group advertisements by advertisement campaign are disclosed. An example apparatus includes memory; instructions in the apparatus; and processor circuitry to execute the instructions to determine pixel color values from a reference advertisement of an advertisement campaign; remove bits from the pixel color values associated with the reference advertisement; determine a first color proportion corresponding the reference advertisement based on the pixel color values; associate the first color proportion with the advertisement campaign; and identify a second advertisement as associated with the advertisement campaign based on a second color proportion of the second advertisement relative to the first color proportion, the second advertisement different than the reference advertisement.