http://i.dix.im/2014-08-08_2059.swf Shows an unexpected result after using minecart command blocks to set stained glass above beacon lights (the 5th from the left)
This is based on the note here: http://minecraft.gamepedia.com/14w32b, that states beacon beams are supposed to change color instantly.
Can't see the attached video, most probably duplicate of MC-65523