Well...a color changer is somethin like this:
http://www.americandj.com/product.asp?ProductIDNumber=8...Intelligent_Lighting you can link several of them together and with a DMX controller you can change colors instantly and they can all be synced or ran independantly. As for your par can question, Im not entirely sure...I noticed that the 56 uses a slightly brighter lamp. It also might be a little bit larger can. Im not sure tho...check out adj's site and compare the two and see if you can find any differences. Anyone else know of any differences between the two. Oh and if youd eicde to go with the cans remember youll need dimmer pack(s) controllers and cables (this is all if you want to make the controllable. If not then just plug em right into a power outlet and your set! Check out some of the stage lighting also and see if u like any of em.. ANy other quesiotns...we're here to help!
-AMP