UMG changing color via program vs changing it's png file


Simple question.

  1. I have one progress bar for HP.
  2. I wanted to have it changing it’s color when HP less than certain threshold (50% for example).
  3. Currently I’m using same png file with different color for the fill texture.
  4. Would it be cheaper to change the png file with different color or better to use neutral color and change the color via program?

Probably will be different depending on the applications and how many changes needed etc.
I just wanted to know generally which one is cheaper approach ignoring the hassle of creating bunch of same png files with different color.