[Duugu]

This is from the default TargetFrame.lua:

UnitReactionColor = {
	{ r = 1.0, g = 0.0, b = 0.0 },
	{ r = 1.0, g = 0.0, b = 0.0 },
	{ r = 1.0, g = 0.5, b = 0.0 },
	{ r = 1.0, g = 1.0, b = 0.0 },
	{ r = 0.0, g = 1.0, b = 0.0 },
	{ r = 0.0, g = 1.0, b = 0.0 },
	{ r = 0.0, g = 1.0, b = 0.0 },
};

You could change this table.