The original American TV standard and TV recorders were 60Hz. When color was introduced, the frequency was shifted to 59.94 to avoid interference between the co

The original American TV standard and TV recorders were 60Hz. When color was introduced, the frequency was shifted to 59.94 to avoid interference between the color signal and the sound signal. (Color was encoded as a high-frequency sine-wave on top of the black-and-white signal which is mostly invisible on a black-and-white set (which allows for backwards compatibility). The phase of the fuzz indicates hue, and the amplitude indicates color intensity. This is why in the old system, if someone wore a shirt with vertical stripes on TV, viewers would see a rainbow of color over the shirt.)