I’m of the general opinion that learning new things is never a bad idea, but let’s break down your sub question regarding usefulness.

At the very least a basic understanding is certainly useful. I make a point to at least learn alphabets and their sounds so I have a fighting chance putting what I hear into a translation engine. Similarly, Russian isn’t the only language that uses Cyrillic.

Paet that though? In my lifetime it was first unthinkable that I could ever visit Russia, then became possible and even a tourist destination (see: Trans-Siberian rail), and back to basically unthinkable to me.

It’ll most likely swing again.

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!