This was a long time coming as well. The colour represents where, or which bus, that particular item exists on the aircrafts electrical system.
<a rel="nofollow" class="external text" href="https://www.flickr.com/people/44389375@N00">Shawn</a> from Airdrie, Canada
<a rel="nofollow" class="external text" href="https://www.flickr.com/photos/cdnav8r/1245142933/">Coloured Circuit Breaker Panel</a>