You must use the proper paint when painting vinyl shutters. It should be an acrylic paint including a urethane resin, as other paints, including exterior paint will not stick to the vinyl.  You can find this at most paint store though you may not find it at regular home supply stores. You will also need somewhere to hang the shutters while they are drying that is out of the direct sunlight.

Here are simple steps for painting vinyl shutters:

Step 1: Take your shutters down, they are much easier to paint that way.

Step 2: Wash them thoroughly with warm soapy water. Rinse off immediately and then dry them with a soft cloth.  For stubborn grime you may need to wash them several times. Take care not to scratch the vinyl while cleaning them.

Step 3: Set your shutters down on newspaper. Apply the paint to one side, using a spray can or a paintbrush. You will find that you need to use a paintbrush to get to the hard-to-reach areas. Once the paint is dry, turn the shutters over and paint the other side in a similar fashion.

Step 4: Hang the painted shutters up somewhere outside, out of the sunlight, for two to three days so that they can dry thoroughly.

Step 5: Once they have been allowed to thoroughly dry, put the vinyl shutters back up.

This simple procedure can be done on either internal or external window shutters, providing you can find the right type of paint. Another key point to successfully painting vinyl shutters is to paint them the same or a very similar color. For example, you should not try to paint your old brown or green shutters white. Instead, find a shade of paint that is close to the original shade of the shutters. If you do so, your vinyl shutters will soon be looking as if they were brand new.