An easier to modify blog’s appearance

Well, let’s see. That’s not something WordPress does. I’d say your best bet is to check out http://codex.wordpress.org/Blog_Design_and_Layout and learn about CSS. Or, run through the theme browser until you find a template that you like.

I have just run into this:

Typetester

Perhaps, it could be turned into a plugin as a first step toward a future built-in wysiwyg css-editor.