Nice walk through on your side.
The color search mechanism is one that I am wanting to rehash. When the album update script is started, each album's color info is parsed and stored in the database. During the update, they are also assigned a color group which aligns with the color selection in the UI. In my implementation the nearest neighbor was trying to be determined when each album is parsed. Its an area that needs improved upon but that's basically how its setup.
During the research phase, I referenced a php class for the color parsing, but ultimately modified it heavily for my use. http://www.phpclasses.org/package/5577-PHP-Get-the-most-used...