here some info on painting on flex face here a link this might help personally i think you can (but try to find out for sure i dont want you to screw up th panel!) 3m well not recommend it becuse painting would not produce an even illumatated look it would be uneven since you are doing by hand its not consestant.The flow of paint like screening or printing are distributed evenly not like hand painting so i hope this help
http://www.signweb.com/fabrication/cont … 81210.html
heres sevral more links
http://www.google.com/search?hl=en&lr=& … gle+Search
Also here is some contact ifo for 3m canda
http://www.3m.com/intl/ca/english/about … index.html
hope this helps!!