There was a time when there were no separate names for blue and green in the Japanese language. Some languages right now have concepts of fundamental colors like navy blue and light blue, where English rolls it into a single "blue". Naming colors is highly cultural and changes over time. The idea that colors have boundaries is fascinating from both psychological as well as linguistic perspectives.

The framing seems stupid if you take the naive perspective that your language's way of dividing colors is the only valid one. Exercises like this and discussions that follow help expand perspectives.