its use would be for MWO
I believe you are referring to MechWarrior Online, correct? If YES then I just want to reiterate that obtaining this kind of data automatically via VA may be considered a terms of service violation. I don't want to take the wind out of your sails, but I also want to make sure you're fully aware of this possibility. The issue probably won't be that you're scanning your monitor (X,Y) coordinates but rather what you'll do with the data you collect. It looks like MWO is competitive, and having this kind of data might be considered a competitive advantage. The only circumstances I would think you wouldn't have an issue is in a single-player non-competitive environment (no rankings, racing, etc). Might even be a good idea to contact the developer and explain what you're trying to do to get a more concrete answer. Or if you don't care, then whatevs. Just my thoughts
So my example analyzes the pixel directly under the mouse. This pixel corresponds to a specific (X,Y) coordinate within your display(s). I'm guessing this gauge you're looking to monitor has a static size that changes color depending on the heat level. That simplifies the problem since then you just need to figure out an origin pixel coordinate to start your "scan" and then create an algorithm to iterate across the pixels that comprise the shape you want to scan. You'll also need to identify the RGB (or hex) values that correspond to the different colors you may encounter on the gauge.
Also keep in mind that your gauge shape and color characteristics may simplify the problem further. I took a screenshot from a MWO video:
So it looks like you're basically going to need to do a simple 1 pixel wide vertical search and look for where the gauge goes from black to NOT black. Or perhaps you can just monitor the red value of the RGB and once it goes above a certain amount you've "found" the heat level. I also included an arbitrary example along with the calculation (yeh math!) to get a heat level percentage.
So once you've identified (X0,Ymax) and (X0,Ymin), which VA can help you gather, you just have to start your search at (X0,Ymax) and use a loop to subtract 1 from the Y-coordinate, get the pixel data, evaluate the data, and repeat until you find the heat level or you reach Ymin. Then you can just calculate the heat level percentage. You could also start at Ymin and work your way up, though I figure you're probably more likely to be above 50% heat than below it so you'll find the level faster by starting at the top.
Hopefully that helps!