Red versus Black

So it sounds like there were mainly functional reasons why red paint was so widely used on rolling stock. Generally speaking, it seems that the two most generic freight train colors have been black and red with the red being in the vicinity of Tuscan red.

Considering that black was also used on a lot of rolling stock as well as most locomotives, was black paint also chosen based on similar functional reasons such as low cost and high durability? Or was the main reason for choosing black based on masking the discoloration from coal smoke or coal dust?

My question about the black cattle cars leads to the question of why most rolling stock was painted in shades of red instead of black.