Looks as though you have not done a proper plug chop. You just went out free riding and decided to look at the plugs. The porcelain insulator on the right side plug looks like it's overly rich from burn which you obviously understand.
The porcelain portion of the plug will tell you a little about mid range but not top end power. The deep end of the plug/top of insulator is the best indicator. Chocolate to white would be nice. Also the burn on the electrode tip will give you good indication of jetting on top end if plug chop has been performed correctly. Even on used plugs, not old, the electrode tip should look to be 1/3 to 2/3 burned white. anything more than that and while the engine does not seize, the fuel mix is too lean.
Keep in mind when running around in the southeast during the summer the weather is very humid. You want more power, dial it in on the high speed mixture screw for less fuel to work with the water in the air. More humidity, lean her out.
Because you are running a single carb, you most likely have week reads in the cylinder you pulled that plug from. It's burning fine so plug cap/ ignition signal is of no concern. The darker plug could just be a sign of weak rings from piston dome collapse sticking ring or that particular cylinder running hotter than the other. All depends on how the cooling is moving through head.
No two carbs are going to be made alike, so in the event it was a dual carb boat, I would be playing with throttle valve sync or dialing in main jet and high speed screw to get equal burn. If you were racing you would re check deck height between each cylinder, check squish or even index the crank to see there is no torsion on webs. Short rods, short pistons can all lead to poor squish/ deck height. No worry just tune second carb to make it look right.
If it was a triple cylinder engine outside of the world finals, I'd let that fugga run a little richer.
Disclaimer:
Newbie under the sauce and fair two stroke tuner. :Banane37:
