Tan and dry sounds normal. You'll notice that too rich shows black and dry like in the picture. Unless you see black (not blue) smoke coming out of the exhaust during normal running or acceleration, it probably isn't fuel fouling. Too much fuel will also show up as a heavy, black, dry soot in the tailpipe. Black and wet (oily) indicates an oil problem.
If they truly are tan and dry, I would not lean it out any more yet. Idle mixture is easy to set and generally won't cause any plug fouling unless it's really rich and spends a lot of time idling. After initial idle mixture is set, by just slowly turning them in until the engine starts to stumble, then backing off a 1/4 turn, leaning them out more will have little to no effect on the plugs. And idle mixture itself will have no effect once the RPMs are increased when driving.
Pictures would still help.