I did not watch the videos yet but I did look over the written description on the website for "The sound of Color".
Assigning a sound to a color is in line with using the opposite to teach yourself perfect pitch from years ago. I think it was Keven Burg?
Any way the idea was to associate a Color to a given pitch. The color was not a set in stone association for all people but each individual would choose which color best represented a specific pitch. Associate one pitch at a time and learn to recognize the pitch by similar attributes between the two. For Example, maybe F# is Bold and vivid to you and you sense the same thing with the color RED. Perhaps Ab always sounds Muddy and Dull, so maybe that would make you think of Brown.
To be honest it is just another way for you to pay closer attention to sounds and frequencies and to notice slight differences or characteristics between them.
Granted it is not the same as having a chip implanted in your head that when you hear F# you would actually SEE red, but the Pitch can still be visualized in your mind when you hear it.