Possible to change background color from orig. oH themes like Orange Tree or Pale Blue?

last two years I only use the BasicUI on my Tablet, now I start with HabPanel to get a more modern and bether and design,

Is it possible to make “small” changes on the themes coming with OpenHab?
I.e. just change (modify) a little the background color etc. …
(and yes, whne update is coming these change will be lost).
But is it possible, or are the colors in lot of files deployed and not easy to change in one css (?) file ?

And: Is it easy possible to add other complete and direct usable themes? Without manual copying lot of files and buying needed icons etc …? But actual i just need small changes on the main color from the provided themes)

I don’t know about full themes, but you can reference an external CSS file in the HabPanel settings if you just want to change some of the colours. See “Additional features and settings”.

I also found these instruction and information ,
but is there a simple example how to change “simple” the defined colors from a provided theme?
I have only very basic css knowledge, so i.e. I don’t know the css “variable name” to overwrite in the my additional stylesheet.

Actual the Habpanel (with theme “Pale Blue”) has a dark blue background (nearly black), and a blue font color. (see picture).
I will change both a litte bit brighter (so also the values are better readable, more contrast).
That’s all.