Apart from that, if “useless” people truly didn’t have a purpose, then why did nature make them in the first place?

This won’t work on this sort of person. Failure is a personal choice in their narrow world view.

Red, orange, yellow and green are all the same varient, but at different ripenesses. The others are different varients.

Mostly just a novelty. Throw in a bit more colour, if available.

Not sure I’ve seen an orange, white, brown or purple traffic light before!