Not exactly sure what you mean when you say "white reverse text", but I'll give this a shot.
If you go to Composition --> Composition Settings or with the comp timeline selected press cmd-K, both will bring up the Composition Settings panel. In there you can change the background to whatever you want. You can also hit the Toggle Transparency Grid button at the bottom of the Composition panel and that will toggle between the Composition background color and a white and gray grid. That might make it easier to see what you're doing.
Or what I always do is just make a new solid, choose a color, and make it my background layer. Change the color whenever you want.
You can edit text color easily by selecting the color in the Character window.
Hope that helps!
Thanks for your quick reply.
I need to take the time to learn ae properly:-)