I think you would have to apply a type of primer, something like epa primer and then you would be able to apply almost any type of finish.
The secret of applying a painted finish to plastic is, it needs a sound base for adhesion, without a quality primer the painted surface will [For want of a better description] peel and mark more easily.
I would stay away from emulsion, this would be a poor finish for someting that is gettting handled on a regular basis and would not last very long.
Ok i work in a body shop. Tape up anything you dont want painted. Now take some scotch bright and ruff that bad boy up (this is very important) Now any spray, brush paint should work. Just as long as its scuffed up a lil. So go to your local store and nab a can of flat black and spray away my freind. Acrylic isnt the best paint to be painting computer parts with as it scrathes off very very easily and mars up. Use laquer based paints.
Ep, glad to see you come back and tidy up...did want to ask a one day favor, I want to enhance my resume , was hoping you could make me administrator for a day, if so, take me right off since I won't be here to do anything, and don't know the slightest about the board, but it would be nice putting "served administrator osnn", if can do, THANKS