Color Phi Phenomenon Psychologists Paul Kolers and Michael von Grunau investigated the phi phenomenon in response to a question from the philosopher Nelson Goodman. Goodman wondered what would happen if the circles changed color, going from red to green and vice versa.
Subjects often report being able to see the circle change color in midstream.
This question can be raised for any version of the phenomenon. This question is addressed in several accounts of the phi phenomenon.