Two plug threads going.... eeekkkk.
Is there a difference with plugs even with the same numbers?
Generally speaking, the numbers represent the heat range and in compatible/matching plugs they mean the same thing. But, sometimes in a stock bike that is a little old in the top end, people run hotter plugs (8 or 7 which is hotter) to help the ole' betsy to run right and not foul when putt putting around.
bottom of plug was an aluminum-colored silver and my old ones from the bike shop were a copper-color.
Sometimes that is purely manufacturer preference on colors.... sometimes to help identify the plug types (quality in a brand) at a glance or for wow factor....
The electrodes (center and ground prong) materials are the biggest difference in the plug type classes.
Sly