H1 - H6 in Stream, Post and Pages

How and where can I edit the H1 to H6 tags, I mean <h1> should be the same size around the whole template.

At the moment <h1> is smaller in the headline of a post as in the posted text itself. Why?
http://pronatur24.eu/werbung

Is the headline of a posting in the blogstream and post itself always <h1>?
And how can I change the color on both sides?
http://pronatur24.eu (blue)
http://pronatur24.eu/2012/der-grosse-bioschmaeh (green)