I think that the sky and wheat are what is represented by the yellow and blue stripes in Ukraine’s flag, and that they are thus doing a literal version of same.
The first national flag for Ukraine was adopted in 1848 by revolutionaries who wanted its western parts to be freed from Austro-Hungarian rule. They based their flag, consisting of equal horizontal stripes of yellow over blue, on the colours of the coat of arms used by the city of Lviv. The arms showed a golden lion on a blue shield, an emblem dating back many centuries. Late in 1918 the decision was made to reverse the stripes of the 1848 flag to reflect the symbolism of “blue skies over golden wheat fields.”