The error is pretty clear about that. The problem is not you setting the color but the addon !Colorz trying to call SetTargetClampingInsets. That function is protected now.
With 7.1 some of the nameplate related function calls become restricted.
http://us.battle.net/forums/en/wow/topic/20749494846
On that note. You can build nameplates with oUF now.
http://www.wowinterface.com/forums/s...ad.php?t=54584
If you are already using oUF for your unitframes you can get rid of the second set of unit event handlers and use oUF for all units.