The engine will leak oil from time to time.
What colour the oil is will determine what the problem is.
If it's black, sticky oil, then it's excess unburnt two stroke oil. This is normal.
If it's a slimey bronze oil then it's gearbox oil, the engine is designed to run excess gearbox oil over the chain before leaking to the floor, again this is normal. If the amount of oil being leaked is excessive, then either the gearbox has been over filled, or there is an underlying problem.
I realise this is an old thread but if anyone else is searching common problems....