just got my oil changed and I just checked it:

#1 Very dark for an oil change 3 days ago

#2 level is fine


what internal problem would cause the oil to blacken so quickly?

The car was not maintained properly(oil changes regulary & on time) Its called sludge. The best way to get rid of it: tear down the engine & clean it(interanlly). You could use an enginel cleaner that you pour in the oil & run engine for a few minutes, then change oil. There is only 1 bad thing, if there are any leaks they have a chance of getting worse.

How many miles are on the car/engine?

142,000 kms

I had an engine flush roughly at 135,000 kms