Oil Color

[Dan DiBiase]

I thought this had been discussed sometime but I  searched in the archives and came up empty so..... I had my 25k mile  oil and filter change done (at the dealer) about 1k miles ago. I was  checking the oil yesterday and noticed that it seems to be pretty dark,  almost black. Up to this point I have used Mobil1 0w-40, but forgot to  buy it before I went to the dealer. Their standard oil is Castrol  Syntec 5w-40. I thought I had read somewhere that synthetic oil tends  to darken more quickly....? Does this make any sense? 
  
  Thanks...
  
  Dan D
  '04 A4 1.8Tq MT-6
  Central NJ USA