Abstract thinking is essentially what makes us human, and cave art, specially negative hand stencils, are some of the first demostrations of it in the archeological record. Something special about these hand prints compared to other styles of cave art, is that they have been done by isolated humans all around the world using basically the same techniques, almost like if it was something intrisically human.
The colors used are colors that were easily available to early humans, and are the ones usually found in this type of art
Own work, from Reddit.
u/Caribbeandude04