Can we change the colour of Progress bar filling blocks

I have a progress bar. I want to change the colour of the blocks that fill up the bar gradually. Is it possible?

One way to accomplish this is to use a custom progress bar that handles
its own painting. This site has a few in the 'other controls' section. The
gradient progress bar works fairly well and allows you to set the two colors
it fades between. This bar will be drawn smooth also, not the blocks.