> If all this were generally true of blue light, then a television monitor tuned to an all-blue channel would be just as effective.

If it hits the same frequencies.

The frequency of the light is important here, because our body/eyes pick up on and react differently to, well, different frequencies. Just because we perceive two lights as producing the same color does not mean that we will get the same reaction, physiologically, from both of them.

An "all-blue" channel is an artifact of your television. Modern televisions put up a solid color rather than snow when they fail to detect a carrier wave on the chosen channel.