How to mix bars (health and poison)

I’m looking for a way to make a mix stat bar. That is a health bar that changes color duo to poison/infection level of a player. Also making the poison level decries health faster at higher level.

this is a very simple UI behaviour that can be accomplised by use of variable being passed into your widget. I imagine there are lots of tuts that will help with this. I suggest you start looking at tutorials as this is a simple task and you will run into much harder machinics as you progress.
try this

Once you pass a variable into the widget (as suggested above), you can animate it like so:

At the same time you can MapRange the health value to Lerp between colours.