I basically want to create a full screen window and draw text on it in different colors and sizes (and also update the screen). I've used pygame for this in python and I'm looking for a similar library (should be fairly easy to use).
+1 if it handles input too...
If you're looking for a specialized game library, you have a number of options that you can find here. FunGEn is probably your best option out of those libraries. However, your question seems to suggest a game library would be a bit overkill, if all you're looking to do is draw text and receive input. In that case, you might opt for something simpler like HOpenGL or hsSDL. There are also several other libraries listed here.
Edit: After a bit more research, you might do well using haskgame. I've never used it myself, but it looks like it's got a few functions here that do exactly what you're looking for.