Today I painted my monitor.
Obviously, because my monitor was the standard beige colour to start off with, it stuck out like a sore thumb when placed inside the cabinet.  Now some people on the internet have gone to great lengths to strip down their monitor and mount it inside their custom built cabinets, however, my quick sizing test showed me that the monitor fitted very nicely as it was.  So, I simply masked off the monitor to protect it's insides then applied a couple of coats of primer.  The primer I used was white primer from Games Workshop.  I chose this because it is a very good primer that can be used on metal or plastic and fairly cheap at only £5.00 per can.
Once the primer had fully dried I applied the black top coat. A standard Holts car black paint was used.
Starting with a couple of very light dust coats and allowing to fully dry between allowed me to slowly build up a full even coating over the whole monitor front. Once installed back in the cabinet, the final result is brilliant. My spare monitor now looks made for the job!

Oh and before I re-installed the monitor I corrected the angle of the shelf for a near-perfect fit.  The monitor face is only about 5mm away from the glass now!