We all know and love the russian tri-color: white, blue and red, possibly with the coat of arms in the middle:


By the way, it was a surprise for me to find the old Russian flag, which is black, yellow and white:

Anyway, I could not help but notice from the footage of Russian soldiers in Ukraine, that some of them have a modified flag. The white stripe is replaced with black:

I found it fitting, in that black is the color of mourning and the Russian Federation is mourning the war in Ukraine, and the whole new world order. But primarily the Russians are mourning the ongoing war in Ukraine.
I also thought, perhaps the change was made by the soldiers for pragmatic reasons: white is the most visible part of the flag, and by removing the white, they crease their visibility and increase their safety.
I also saw a variation at least once, where the white was replaced with green:

Green being the camouflage color, I would assume that the change was done to reduce visibility to increase safety.
From the stylistic point of view, I like the black variant better than the green one.