Make a stencil, and custom spray paint your laptop.
Step 1: Design the template
Bold designs work best. Try to keep all features larger than 0.150 inches.
This one is designed such that you can cut it from one piece of material and then snap in the interior pieces to do different layers. Since you never have to remove the first layer, the subsequent layers are already aligned.
If you are going to laser cut the template, make sure your design is in a vector format. Programs such as Adobe Streamline can turn bitmaps into vectors.
Step 2: Make the stencil
Cut the stencil. Printing the design and cutting it by hand is a good option. Adhesive stencils help prevent paint wicking from underneath.
I elected to laser cut a stencil from 1/8 thick acylic. I wanted to reuse the stencil and have relatively small, sharp features.
Step 3: Test stencil
Test the stencil and your technique before painting your laptop. I have had limited success cleaning up mistakes with paint thinner and a small foam brush.
Step 4: Clean laptop
Clean the dirt and grime off our your laptop with acetone, rubbing alcohol, or soap and water. Be careful though, one (or maybe all three?!) might dissolve your laptop! A little bit of acetone on a paper towel didn't harm my ThinkPad.
Step 5: Position the stencil
Position the stencil and cover and exposed areas with tape. I used some lead weights to hold the stencil flush against the laptop. Place lead weights carefully!
Step 6: Paint first layer
Paint the first layer with thin coats of spray paint. For me, the first layer is the green outline. It's important to spray multiple thin coats several minutes apart. You don't want the paint forming droplets that will wick underneath the stencil.
Step 7: Thin channels and thick paint
I was tempted to place interior parts on this first stencil. The thin channels didn't get much paint in them until I lost patience and really gooped the paint on. It then wicked under the stencil and made a mess.
Step 8: Place second layer stencil
The second layer only covers the green outline leaving the interior open to be painted purple. After using it a few times you may need to scrape the paint off of the edges for it to snuggly snap into the first stencil.
Step 9: Paint second layer
Paint the second layer with multiple thin coats.
Step 10: Place the third stencil
Scrape paint off the edges if necessary.
Step 11: Paint third layer.
Paint the third layer with multiple thin coats.
Step 12: Remove stencil and tape
If you're careful, you don't need to wait for the last layer to dry before removing the stencil.
Step 13: Be the envy of your friends!
Can't get any color on your laser-etched powerbook, can you?!
A clear coat might be a good idea, but I figured the paint will eventually chip off and I'll just repaint it with another design.