As the title suggest, I would like know the motivation/ historical background why chromatic homotopy theory is called 'chromatic'. Literally, what analogy to colors it might have. Accordings to wikipedia the origin of such homotopy theories bases on Quillen's work on cohomology theories of formal groups. This allows due to wikipedia to study that studies complex oriented cohomology theories from the 'chromatic' point of view.
This involves classification of these theories by so called 'chromatic levels'.
Has this 'visualization' regarding the theories as 'lying on certain levels' some funny analogy to colors regarded from physical viewpoint as a part of electromagnetic spectrum? Sound probably silly but I am quite curious what was the background for the choice of the name 'chromatic' in this context.