you never said if you did anything to the carb. did you jet it down to clean the plugs up?

is it possible the carb is rich at idle and transition and lean once it gets on the mains (your jetting)?

the color difference on the two plugs you showed doesn't seem that drastic to me given you have a dual plane manifold.

if it were me i would jet the carb up 4 steps, let it get wamr, then set idle speed and adjust idle mix to the highest vacuum reading, then go see if it's still missing.
it's a simple thing to check.