The rule is – there is no rule. All depends on what works for you and what parts you actually have. In general, sort by part first, and then by color if you need to.
if you look at the sorting hierarchy tab in the lug inventory tracker, you’ll see how the lug inventory is sorted
https://docs.google.com/spreadsheet/ccc?key=0AszRIVULP9QidF9TWnVTbV8xMEltSWZxSzI5WFREbGc&usp=drive_web#gid=0