color swapping

[malymin]

The thing is that a red/blue color channel swap has the highest chance of looking good because of luma. The difference between the luminosity of RGB "red" and "yellow" and the luminosity of RGB "blue" and "cyan" is similar, so they both create a pleasing dark-to-light shading gradient that looks natural:

r	o	y
b		c

Meanwhile, RGB "green" is very similar in luminosity to "yellow" and "cyan", so a red/yellow gradient made green/yellow often looks "flat" in its shading. The same is true for RGB "magenta" being very close in luminosity to "red". When it comes to blue colors... the blue/magenta contrast is stronger than the red/magenta one, but the green/cyan contrast is weaker than the green/yellow one.

r		m	b		m
r	o	y	b		c
g		y	g		c

Anyways, this is why the colors on a TV broadcast test card are always arranged in the order they are: it's from brightest to darkest luma of pure RGB hues!

y

c

g

m

r

b