How do I change the image a resource bar is using when it gets to a certain size

Like how in Pokemon where when HP goes to 50% the bar turns yellow and then red when really low.
NOTE: I do not want the bar to constantly be all three colors, it should ONLY change color when it reaches the point where it should change.

Not sure, but I think if you are using a pre made asset it’s not possible. You have to make your own from scratch. Make it white and change its color to wathever you wish at the beginning of the scene. During the game change colors according to its lenght. If you don’t make it white it wont work.

Easiest method: Have your base asset be white, then use the Tint action to tint it whatever color you want based on the current HP

More complex (but slightly more flexible) method: Use the color replacer effect on the object and replace each color you want to change, then use events to update the color replace colors to whatever you want.