system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: Why are Brown, White, Black and Green common surnames but Red, Blue, Yellow, etc. aren't?
gpt
They are surnames in Germanic countries because they are also shorthand for jobs - white signifies a silversmith, black signifies a blacksmith, green signifies a gardener, brown a farmer. 
"Gelb" is German for Yellow, and turns up in Germanic names, and Blau does too, blaustein, blaupunkt, blauenfield. Rot is German for Red, and also shows up in names. Redfield, Redstone, but also Rotterdam, for instance. They aren't standalone because there was no trade significance of a profession to them - blue is the colour of the sky, red the colour of fire or blood, yellow signifies gold. Orange was considered either red or yellow, traditionally, and purple was usually reserved to signify royalty.