He got CMYK and subtractive color completely wrong, but most people who are not in printing do. He kind of got LAB color right, but was a little wrong there too. Not that any of that really matters for photography, except that if you are sending your pictures to a CMYK output device (inkjet printer, or even a magazine publication), its important to know that the achievable gamut in CMYK is much smaller than RGB. In laymans terms, your photo printed on a CMYK device will look much more subdued when it is eventually converted to CMYK.