What's the reason why English and most other languages of Europe treat blue and green like distinct basic colors, while many languages of Asia have one word encompassing both? What's the reason why Hungarian has two basic words for different kinds of red? It's just a historical artifact of language evolution. Russian happened to the evolve two different distinct basic color words for blue; to an English speaker, both are different shades of blue, but in Russian, neither is a shade of the other; and Russian has no single color word encompassing the English concept of "blue".
Even in English, in certain contexts, blue-green middling shades are treated individually (turquoise, cyan). Of course there are many color names in paint/art, but even in everyday situations there is a pretty clear concept of turquoise being its own distinct color.