Black oil after 60 miles

Hello,
 
I have a question, I put nice clean oil in my engine, but after 60 miles or
so, it turns black.
 
so, I have questions:
- is it normal?
- where can it come from?
  - I know that I run a little bit rich, but it is the best running setup
for my car
- could it be because of blow by? my compression numbers are 100 100 95 90
- should I worry?
- should I change my oil 5 or 6 times every 100 miles or so to see if it
clears up?
 
thanks, cyrille