I assume they meant the unintended rainbow-like color halos and vertical line artifacts plainly visible on a good crt, particularly on edges due to Woz's design where there is no direct pixel color really; rather, a "1" in a specific "phase" (odd or even column) of a pixel byte would tell the TV to output a certain color, like green or magenta. It simply walked the bits in memory as if they were chroma patterns, in rough approximation.

That said I'll read up on the linked article, I could me misremembering things.