Looks fine at the tip, but I cannot see down to the base of the insulator -- is it white all the way down?
If so, I'd expect an overlean condition. This could easily be a vac leak on this car, often around the injector seals (although they don't leak like Volvo seals do).
Do the plugs on the other side look the same or different?
1972 220D ?? miles
1988 300E 200,012
1987 300D Turbo killed 9/25/07, 275,000 miles
1985 Volvo 740 GLE Turobodiesel 218,000
1972 280 SE 4.5 165, 000 - It runs!