Heh, yeah, I like having things neatly organised, makes everything so much simpler!
The colors on the map are completely random... When I was a kid some of my relatives worked in offices, in those times, a office was usually stocked with all these different cards and tags made of cardboard. And it was in all different colors so the employees there could mark their files or charts or whatnot with them. But the colors never had a formal code or meaning they were just there for them to be able to locate the stuff they needed at a glance. So I thought it would be less boring if I gave these cards some color as well.
As for additional reporters alas the answer is also no, the game has a hard coded number of reporters so you can't disable any of them either. But you can tweak their abilities and "personality" a bit. Maybe even change their names? Not sure about that anymore, it's almost been 4 years since then...