Hi esdeb
Blue smoke usually indicates unburnt fuel, So i would take an educated guess that it is over fuelling on start up,Just a thought are you allowing the glow plugs to do there warm up,Or is the cold start at fault on the engine, The usual start on my crdi is after the heater light has extinguished it only has a couple of cranks on the key, Are you finding that the engine is over cranking to start, This would produce unburnt fuel that when the engine starts,This ignites and is blown out of the exhaust, Could lead to a catalyst problem if not sorted, There are more clued up petrol/diesel heads on here hope some one else will be able to shed more light on this for you, White smoke usually indicates a timming issue or a head gasket problem, But as said blue smoke may be less of an issue here,Deffinately needs sorting, Let us know how you get on. Thats what this forum is about sharing helpfull information and tips.
all the best col