Constrained bones are usually colour coded. Using copy constraints to selected from the pose menu does not update bone colours in pose mode, latest svn build. Example Case: Add three bones. On one of them add a valid copy rotation constraint to any of the others. Select the remaining bone not involved in the constraint and try using the copy constraint to selected feature from the pose menu (there is no hotkey by default...?) - note the constraint is correctly added but the colour does not update until a tab into and out of edit mode on the armature.

thanks
Josh