I assume what they meant was that only some colors are pure frequencies, and most are more complex waveforms. As the sibling comment gestures at, "magenta" is

I assume what they meant was that only some colors are pure frequencies, and most are more complex waveforms. As the sibling comment gestures at, "magenta" is the sum of a pure blue wave plus a pure red wave. "Color" also can refer to several different phenomena which were historically conflated in a way that made teasing apart certain observations difficult. It's a property of objects (apples are red), a property of light (lasers are red) and a property of perception (I see red).