It's great, because you don't have to read the var name, you just have to see if there's any var in a function that doesn't have the same color as anything else and they tend to stick out like a sore thumb.

Not sure if that's the best explanation, but if you're using any JetBrains IDE you can try it by going to Settings and searching for Semantic Proximity and hitting the check mark. Easier to show than explain.