Electricity is color blind. This was drilled into my head through my apprenticeship.
Fact is you all can ask for color standardization but the manufacturers will not go along with it. See Trane for explanation. One thing I don't understand is how some will go into great explanation on why T-Stat wire needs to be standard colors regardless of any variables.
However when you get into a unit (ill use the last unit I worked on as an example) a heat pump built by American Standard.
Yellow Wire (Compressor) comes into a mullex plug, comes out Yellow with a Red stripe, picked up HP switch, comes back out same colors, picks up low pressure Blue with black stripe (2 colors that go well.....) comes back out same, then loss of charge switch, solid white... Herm.. white, really? How the #$%^ does this make...
Point is, the Manufactures are having a hay day with the (Hey new guy, pick a color you want to use for Loss Of Charge... CLEAR IS MY FAVORITE COLOR)
At our Company we use this.
Red = Power
Black = Common
Yellow = Compressor
White = Heat
Green = Blower
Orange/Blue = RV
Pink = Second Stage Heat/Cool
Opposite of Needed RV color = Second Stage Heat Cool when needed.
This is our Guild Line, so we have a standard on our installed equipment, makes trouble shooting easy. Lucky for us we have been doing this from 1995 (color standards that is, not 8 wire) so we know our customers well.