This is showing expected threat, or xT, which I had not heard of until now. I don’t subscribe to The Athletic, so haven’t been able to read more than a few sentences of this but if anyone does, this article might explain what we are looking at. Or it might not, I don’t know.
Introducing 'expected threat' (or xT), the new metric on the block
Expected threat is the next big football metric, measuring ball progression and how teams and players get the ball gets into dangerous areastheathletic.com
I don't subscribe either but this video explains it: