Diesel engine oil black in 2 days?...........

[1TUFFUTE]

Um my friend got his small diesel car serviced and had an issue under the bonnet....so while i checked that for him i checked his engine oil......jet black and it was supposed to have been serviced with oil and filter change only 2 days before. IS THIS Normal. Apparently he rang back and it is....and a dealer he rang said the same thing basically. But 2 days does NOT sound right to me.
Any info would be appreciated....taa