Static header bar stays with page scroll

Hi,

I'm seeing two examples of a beautiful header bar that I would like to implement on a multisite. No links are provided because I didn't know if that was appropriate.

PageLines keeps a header with their logo and drop down menu present on WordPress and MediaWiki.

ServerPress has this gorgeous header bar that actually changes colors as you scroll down - but the header bar stays available.

How are these done? (Please don't just say CSS).
Is there a WordPress theme with this capability?

Now - the WPMS plugin allows CSS code to be placed across a multisite and so I'd like to figure out the code and get this for branding purposes across the multisite.

Another option is to use the white label branding plugin by CodeCanyon - unless something like that exists here ...

Thank you for your suggestions