Great Tit / Velika sjenica

The Great Tit is a distinctive bird, with a black head and neck, prominent white cheeks, olive upperparts and yellow underparts, with some variation amongst the numerous subspecies. It is predominantly insectivorous in the summer, but will consume a wider range of food items in the winter months, including small hibernating bats.

So....this apparently strange coloration white (or almost white) with black is due to birds age, the older the brighter and less yellowish.