This is quite fun, and it really shows the power of theming in SharePoint. Sense I’m no CSS and HTML guru anymore, I’m just going to personalize one of the themes that comes with SharePoint Online.
Simply begin by clicking the gear in the upper left corner, and select Change the look.
The Change the look page has many themes you can spin off from. My personal favorite is the Ink theme. I also like the grey color, and the Tokyo layout is just great. When you are done editing, just hit Try it out.
If you then like what you see, press Yes, keep it. If your eyes are in pain, hit No, not quite there, and try over again.
Well, then you are done. Press Home, and refresh your browser if something looks wrong.