Button Color & Header Image

Hello,

I have two questions:

1) What would stop me from changing the button background and text colors? I've edited them in the custom styling area but the site is not reflecting those changes.

2) How can I get rid of the computer with snakes coming out of it and replace that with my own image? Or is the entire block an image that I would have to create/replace? If so, is there a template for that image somewhere in the theme folder?

Thanks in advance,

Andrew