Hi Mike,
I read a story some years back where the enslaved fems had colored tags attached to their collars indicating their status.There was only one Gold tag which indicated a very priveleged status which included the gold tag wearer
being ble to say "No" to certain things and she was served by all the other fems.The Gold tag had to be earned and the resultant competion among the fems for this gold tag was very intense and causd all sorts of wiles among those competing for this collar.
At the bottom of the status tag rankings were those required to wear the red tag.The wearers of these tags had no limits,rights or priveleges and this tag was known as the" red tag of shame" .

In between there were three other colors indicating other levels with respective
privileges and limits.I regret that the website that contained this story has since disappeared,but was wondering if this is what you had in mind as to the colors on the collars?If so i would be glad to see what I can create from this idea for these colors,if you like,just let me know.