How to change logo, colors of font / text and theme elements for specific pages?

How to change logo, colors of font / text and theme elements for specific pages?

Hi.
I want to change some design elements or formatting of text and fonts depending on the page which is shown to the user.
Like Font color, color of line on top of teh template (design element from template "Opora") and maybe logo.
So there should be the standard settings and for 5-10 pages I want to have a special color / design sheme.
I think this should be possible via CSS and HTML settings / coding.
But how to do this and where to integrate which code?
Thank you!