Cliff, I don't want to seem overly argumentitive but....
Here's how printing works which I learned over 40 years ago in high school print shop. We all know that if we print with black ink on white paper we'll get black lines on the paper; we also know that if instead of using lines, we use dots, we can print various shades of gray depending on how close the dots are to each other and how small they are. With shades of gray, we can print half tones, photorealistic pictures on white paper. However, if we try the same thing on black paper (the opposite of white) we get essentially nothing.
But how to print color on paper, a thorny problem? There are really two color systems I'm familiar with, transmitted light and reflected light. Transmitted light comes from the sun, tv screens, movie projectors, light bulbs. It's composed of red green and blue light. From those three primaries, we can see the whole spectrum of color. But because color on paper is produced by reflected light, these colors don't really work and won't produce a full sprectum. We could print on paper using an infinite number if inks to correspond to an infinite number of colors but that's impossible so instead we rely on the *absorbtive* nature of only three colors: cyan, magenta, and yellow, to create a full sprectum of reflected light from white paper. When you see red paper (or red anything, for that matter), it's not red ink but rather a combination of magenta and yellow inks which, and here is the counter intuitive trick, *absorb* all the transmitted blue and green spectrum and allow only the red to be reflected from the paper. If we see green paper it's because the paper is covered with yellow and cyan ink that *absorb* all the red and blue transmitted light and allow only the green to be reflected. You can figure out what happens when you see only blue. Inks absorb color; they don't reflect it. That's the job of the white paper.
The point being that in order to print color, there has to be a white (something that reflects red, green, and blue transmitted light) surface to begin with. Sure, as I mentioned, you can print on colored paper (a paper already covered with some combination of cyan, magenta and yellow) but the results will be poor and the gamut will be very limited. BTW, black paper is covered with equal amounts of cyan, magenta and yellow which *absorb* all the red, green and blue transmitted light. In order to print on black paper, you have to make it white first so it can reflect transmitted light. In reality, equal amounts of cyan, magenta, and yellow don't really absorb all transmitted light (the pigments or dyes are imperfect) and, hence, black ink (being composed of unequal amounts of cyan, magenta and yellow) is used in printing color.
Most of the color we "see" is reflected and is the result of colors from transmitted light (close to pure white) being absorbed by whatever the pure white light (composed of equal amounts of red, blue and green) strikes. When we see something as white, none of the primary transmitted colors are being absorbed and close to pure light is reflected. So white paper isn't so much "white" as it is a good reflector of the three primaries. You need to begin with a good "reflector" to print good color.
You'll notice that dot gain (really only the ability of paper to absorb ink) doesn't come into this discussion at all. The greater the ability of paper to absorb ink, the higher its dot gain and the poorer its ability to display fine detail. Newsprint has a very high dot gain, coated glossy paper has a very low dot gain. In really fine gliclee printing, dot gain is mostly irrelevant since the printing is very close to continuous tone (no dithering, no dots to be seen). Well, of course, there is dithering but its of a much finer order than what we get in lithography. The early Iris giclees actually are continuous tone with no dithering nor dots. The piezo electric heads on today's high quality ink jet printers produce dots so small that for practical purposes they don't exist: continuous tone as a limit is approached. Dot gain,dot density and dithering patterns have nothing to do with perceived color, only with percieved sharpness. The more dots, the fancier the dithering, the closer the print looks to continuous tone, the finer the detail produced.