Oil in my oil burner

[Davidbolam]

I had my car serviced on Thursday. It's a 2008 passat 2.0 tdi 170. 81,000 miles. My question is I went to check the oil yesterday morning and it's black in colour. Is it possible for the oil to discolour this quickly or have the garage either "forgot" to change it or simply haven't bothered. Would any remaining oil in the sump make it so black so quickly?

I have checked the air filter and this has been done so they have obviously done something to it.

Thanks

David