This is very common with turboed engines. When you stop the car and the turbo is still hot, it burns the oil sitting in it (why you can buy units to keep your car running for 5min after you get out so it cools oil). Anyways, this makes a ton of black junk in there, and so a normal oil change will not get all of that out. If you want, you can do two oil changes back to back (maybe 10miles in between), and your oil might look nicer. That is why diesels usually have a high oil capacity (along with higher CR's and more blow by).
All that being said... I wouldnt worry about it. You can go get analysis' done and look at the oil that way, but color alone wont tell you much about the oil. Also, synthetic vs dino, has very little to do with this.