I'm not disuputing that just because we can't see a particular wavelength doesn't mean it's not there. You miss my point. What I am trying to express is that colors exist only in the human mind. It is the way we have evolved to discriminate between photons of different energy levels, or wavelengths. But, our frame of reference is due largely because we evolved under a "yellow" G-type sun. What we see as "red", for example, may be perceived by an alien race as their equivalent of "blue", for example. Their visual "window" may be shifted with respect to ours. Like the people I mentioned in a prior post who see colors differently than most of the general population, our "rainbow" is just a psychological manifestation. The "red" we associate with hydrogen-alpha light is only "red" in our brains. It's the color we evolved to discriminate photons at that energy level. It doesn't mean that hydrogen-alpha emissions are perceived as "red" by all organisms with eyes. You can only quantify "red" with respect to the rest of the color palette. "Red" only exists within the framework of human perception. Here is the real key: *There is no instrinsic value of "red".* At least outside of poetry and prose, lol. The CMOS chip in your camera records energy levels only, not "colors". Humans have assigned colors to those energy levels based on our own perception, which is the way it is due to evolution (environment), not an absolute expression of what colors are. You can then see how color balance becomes a matter of balancing the ratios of the wavelengths present in the image with respect to one another. What "color" we assign to those is strictly a matter of psychology, not some universal absolute. Does this help any?