Let your mask dry overnight. It may seem pretty dry after a few hours, but it really needs to be left alone overnight to create a nice, hard shell. Once it is dry, you can cut the eye, nose and mouth holes to form frowns, smiles or whatever you like.
What you do with your mask is now up to you. If you want to paint it, use acrylic paints. Watercolor paint will not be thick enough to cover the words and pictures on the newspaper pages.
For masks with horns, teeth, wrinkles or other solid features, you can mold additional paper mache onto the mask when it's done, like this Harry Potter Death Eater mask.
If you want to make a mask but don't want to mold it to your face, try using a balloon, instead. Here are brief instructions on using a balloon for paper mache masks.
Want to know how to make a specific kind of mask? Ask me at our DIY Fashion forum. I will personally answer any questions you have about making masks.