How to make logo area bigger

[TheRealityBuzz]

I've come across something that has been driving me crazy with themes. Half of the theme's area's for logo's aren't big enough. I need room to work with something but its just not big enough. How do I make them bigger? Also how can I change the header colours in my themes? Like where it says start a new topic in fourms.

[TheRealityBuzz]

Whoops wrong area, sorry! Will put it in the correct one.