...surfed to a German Vespa forum :
http://www.vespaforum.de/viewtopic.php?f=17&t=1147
...remembered i had an unused Motip satin black spray can and did this :

Very easy :
1 Remove the "nose" using a flathead screwdriver to remove the Piaggio logo and a Philips screwdriver to remove the screw holding on the "nose".
2 Remove the "headset" :

3 Remove the dashboard. 4 screws & 3 electrical plugs + speedocable
4 Disassemble the dash and paint :

I used tape to mask the chrome bevel around the instruments.
What also should be nice -i think- is to paint it in the same color as the body...