The reason that you will see a red white and blue flag, after staring at a yellow, green and black flag is explain by the of color.
rod and cone
trichromatic
opponent-process
all-or-nothing

I am pretty sure it is the trichromatic theory because all or nothing is about neurons, opponent process wouldn't be it, Rod and cone is about the light we take in the colour etc. I would go for trichromatic. not 100% though

The president's only official legislative duty is to sign or veto bills.