You might find it easier to hire out the task of creating a style for your site to a 3rd party developer in the future.
Using the search feature here, the topic on adding a logo is covered numerous times (the latest such posting on the topic would be
clicky).
As for changing the colors, you'd enter the style editor and change the hex color value for the varying areas to be what you want it to be; there are several online utilities for finding a hex code (
clicky).
