to add colors to the value, if you know which div it is exactly, you can use the class or id of that div in the selector instead of ".label-wrap .t-label" as in step 1 of the example. Or you can look up the class or id by using inspector tool (Ctrl+shift+C) in the developer tools (f12) on your page and then use them in the selector.
If you require more assistance please provide screenshots of div you want to color, would provide more clarity how to change the selector accordingly.
I would recommend you to use the new FreedomUI pages on the site. You can change bg-color in the system settings on the FreedomUI page (on your screen shot I can see Classic UI). It will take 10 min maximum.
To change colors with FreedomUI :
1) Open System designer -> Advanced settings
2) Find the Custom Object CasePriority or create a replacement:
3) Add the new column -> Other -> Color:
4) Add Title to the new Color column on the same page
5) Click on the Name of this object and choose value (Title name from p.4) in Color field:
6) Publish this object
7) Open System Designer -> Lookups -> Case priorities -> View -> Select fields to display: