Doesn't matter if they are hot or cold.
Plugs look sooty to me, not oil wet, and they aren't carbon fouled but they aren't far off, so probably rich. When was your air filter changed last?
What size are your jets? should be 75 main, 40 low speed for the 400f accoring to old posts on this forum. Somewhere on the jet there should be a stamped number.
Let's try this: put the carbs back on, make sure there are no air leaks. Clean the plugs with some carb cleaner. Leave the airbox off, and go for a rip on the highway and see if you are getting the same problem. I have a feeling someone jetted your carbs for pods at one point and may have left them in when they couldn't get the pods to work. Or they could have accidently made the jets larger when cleaning them by using incorrect tools (this is actually quite common) to remove blockages (solvents and air are the only things you should use, those little carb cleaning files can open your jets right up if you don't know how to use them).
I am still hedging my bets that this is an ignition problem, a weak spark can cause an incomplete burn and/or the plugs to load up, as can mistiming from a stuck advance unit. But just to be on the safe side, check the jet sizes anyway. Do you have any other mods to the bike? exhaust?