You can too ask for "red gold" at a jeweller's. Designers use the subtly different colours to good effect, as in the watch chain described above, or a ring I have which is three linked rings of red, yellow, and white gold. In the 1841 fairy tale King of the Golden River Scottish author John Ruskin imagines a "very odd" drinking mug among "some curious old-fashioned pieces of gold plate":

"The handle was formed of two wreaths of flowing golden hair, so finely spun that it looked more like silk than metal, and these wreaths descended into, and mixed with, a beard and whiskers of the same exquisite workmanship, which surrounded and decorated a very fierce little face, of the reddest gold imaginable, right in the front of the mug, with a pair of eyes in it which seemed to command its whole circumference."

I agree with McGrath of Harlow that the phrase "red gold" sounds significantly more evocative than "gold" alone.

I seem to have heard another old phrase, "good red money," which I associate with traditional English idiom. I suppose "not a red cent" would refer to copper, but I believe "red money" carried too strong a sense of value to mean copper coin. But maybe I'm imagining the phrase having any other meaning than "tainted with blood".