Another way is to forego using a color when you really mean a number. The gray I was using RGB(175, 175, 175) actually corresponding to the number .6863 (approximately). So if I just use a math node to plug that value in, I get what I wanted.

Too bad there is no Simple_Number node. Using a Math node is a teeny bit of timewasting, just to get a number in there.

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Renderosity forum reply notifications are wonky. If I read a follow-up in a thread, but I don't myself reply, then notifications no longer happen AT ALL on that thread. So if I seem to be ignoring a question, that's why. (Updated September 23, 2019)