The reason for the blue/brown is due to some common colour blindness seeing red and black as the same colour.
Another example of snowflakes interfering. A colour blindness test used to be part of the interview prosess before being offered an apprenticeship ,fail it and your out.But of course failures not allowed anymore.
10% of men are red-green colourblind. It's not a small amount of people to reject.
I doubt that has anything to do with it. The idea that true colourblindess is common amongst men is a largely myth. The type of colourblindness which would make it impossible for someone to distinguish red and black, or even red and green is comparatively rare.
Colourblindness is a misnomer. It's true 10% of men fail the colourbliness tests, but that doesn't mean they see the world in greyscale. It's more subtle than that. The most common form of colourbliness is deuteranomaly which is very mild and often given the name red-green colour blindness, but it's not that simple. Most people with deuteranomaly can still distinguish between red and green.
Deuteranomaly is simply an anomaly in the green pigment in the cones of the retina, which shifts their response towards the red end of the spectrum, making it more difficult for someone with this condition to distinguish between some hues in the red-green end of the spectrum. This isn't a problem with bright colours: theey will still be able to tell the difference between fully saturated red, green, orange and yellow, but darker shades can be more challenging to differentiate.
Like many men I have deuteranomaly, but I can still use the resistor colour code in well lit conditions. It's only a problem when it's a bit dark or the paint is poor quality. Some cheap resistors use a dark red paint, which often looks like brown and the yellow often looks like green on blue resistors.
If an optician tells me I'm red-green colourblind, I correct them by telling them I'm brown colourblind. If they don't believe me, I prove to them I have no problem distinguishing between red and green objects, but might struggle with dark red and different shades of brown. Obliviously being brown colourblind means I can't be racist.
![Wink ;)](https://www.eevblog.com/forum/Smileys/default/wink.gif)