Dzien dobry, wszelki. Jak sie pan miewa?
I don't really know how some families develop a 'really' blonde gene, as opposed to blonde/brown, in Eastern European countries. Hungary seems to have a larger percentage of white-haired's compared with other Eastern European countries. Though I'm sure a photo-gallery could be provided on their dark-haired populous

, there is a linguistic link to back this one up. Hungarian is linguistically linked with Finnish (way back), and Finns most certainly have more blondes than Poland.
Though the court trial is over in relation to 'most' Poles being blonde, there is a minority who seem to have strikingly light coloured hair. Norwegian like. I'm guessing that the Norse conquests made their way into certain parts of Poland.
My question; Is there any minority group in Poland which acknowledges any Norse ancestry?
Side note- I do like your photo evidence,
Guest 
. But to play lawyer for a second- I'll pick you up on the fact that those Russian soldiers' hair ...is bleached.

(though maybe you knew that).