The article notes:
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Almost the only “scientific” reference that Erikson provides in his book is from a book written in 1928 called the Emotions of Normal People, by American psychologist William Moulton Marston. Moulton hypothesised that our behaviour is influenced by “psychonic energy” that is transferred through a web of nerve cells that he called “psychons”. The four personality types (yellow, green, blue and red) arise, Marston claims, as variations between different people in the structure of their psychonic network.
This “theory” is pure speculation on the part of Marston. There was no scientific evidence for psychons or psychonic energy in 1928 and there is none today. At the time of publication, the science of psychology was in its infancy and, like Hippocrates and Jung before him, he had created a theory without proper scientific grounding. Unlike Hippocrates and Jung though, Marston’s theory garnered little attention, and he left psychology. He later rose to fame though when he created the comic book hero Wonder Woman!
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It might be helpful to simplify life by bucketing people into 'personality types' but there doesn't seem to be any more scientific justification here than one would find in Astrology or Harry Potter Houses (anyway Astrology is a based on a much larger heap of unscientifically collected anecdotes).
