Is there an addon that will highlight, color, or in some other way, identify the fishing pools on the minimap?
There is an ability available in the game without need of any addons. You’ll need to learn it from an Angler’s Guide which is sold by fishing trainers.
Gathermate 2 will mark fishing nodes (and any nodes, but you can configure to show only what you want) that you’ve already fished. You do have to “find” them first though, and it shares across characters.