Yeah, Master Colin is being compared with King Edward. It represents Master Colin's lordship over the household. If you read the book, you'll see that Lord Craven gives his son absolute power to control the house as he pleases while he's away, and no servant is allowed to disobey Colin's orders. This isn't quoted word for word, but it goes something like:
Martha: "You met Colin? Oh no! I shall lose my place for sure!"
Mary: "He wants you to come and call me, the next time he wants to see me".
Martha: "Noo! Mrs. Medlock'd fire me for sure! I'd lose my job!"
Mary: "You said that everyone is obliged to do his bidding, didn't you?"
Martha: "Aye, the wicked boy!..."
Mary: "Well then if you're doing his bidding, you won't get fired!"