Red Blue Refactor

As far as I can tell, the mantra "Red Green Refactor" is derived from the colors of the UI controls in the early GuiTestRunners, which were influenced by the conventions of traffic control system, which perhaps were influenced by railroad control systems.

(Image from JSquaredZ).

As labels, `Red` and  `Green` are fine - they are after all just hints at a richer semantic meaning. 

As colors, they suck as a discriminator for the percentage of the population with Deuteranopia.

Looking for another color pair to use, I'm currently thinking that past and future are reasonable metaphors for code improvement, so I'm leaning toward a red/blue pairing.

(Image from Wikipedia)

Of course, in English, "past" and "passed" are homophones, so this perhaps only trades one problem for another.