That's probably not because of good insulation, but just because of central heating system in most of the apartment buildings

No one have 27 words for snow, that's a myth

Pokój is also Slavic. In Russian related word means something closer to "calmness" and sometimes has overlapping meaning with English "peace". Like "peace" in "peace and quite" for example will be translated with "pokoj", while "mir" in the sense of "peace" means only the opposite of "war".

I assume colors show the original meaning of the word, not the language family.

In Russia as well. And it's called simply "birch juice"