Not sure if its possible to change color of the form control progress bar, maybe with CSS. But its just a guess.
You can turn a sprite into a progress bar like this:
Sprite width = 500 (Just the original width of you sprite)
Max_health_Player = 100
Current_health_Player = 20
Set Sprite.width = (500 / Max_health_Player) * Current_health_Player
In this case the Sprite width would be 100 px
If Current_health_Player is 50 the width would be 250 px