Silver ring around start button?

yes you can put tape between the button/Silver ring; itself all the way around then tape over it completly leaving the ring only exposed.. and then paint it..

you have to take button off completely and disconnect the wire behind it.. "white clamp"

 

You'll have to sand the ring before painting, or the pait will peel off easily. It may peel off easily even with sanding... but you're more likely going to have the paint adhere to the ring only after the ring is sanded.

The best thing to do, is tape it like you're getting ready for paint, use painter's tape, green or blue. put 2 layers of tape on.
Then use a scotch-brite pad, a standard green pad from Wal-Mart will work, unless you have an autobody / automotive paint supply store near by, then I would recommend a "Gray" scotch-brite pad. In the autobody world the colors indicates the coarseness of the pad.
gray = 1000 grit sandpaper,
Red = 320 grit sand paper,
Green isn't really used in the autobody world, but I would estimate that it is some where about 220 or 180 grit sand paper. 80-180 Grit, is extremely rough, 1000 grit is fine, 2000 - 3000 grit is extremely fine sandpaper.

After you get the ring sanded, remove the tape and re-tape with fresh new painters tape.
Spray in light even coats, about 3 coats should do, wait about 5 to 10 minutes in between coats.
Make sure to paint outdoors where there is plenty of ventilation.
Hope that helps!

 

I'm Thinking mask off with tape and use a wide tip permanent marker. A Sharpie would probably show the strokes to much!

 

A paint pen would take just as much work and provide superior results. Visit your local craft store to see what's available.

Galaxy Nexus ? 2

 

I would use double sided tape and black construction paper to cover the entire switch.