Power-flow-card-plus change color dependent on darkmode

Configuration Frontend
1

I want to change the color dependent on darkmode.
That is the standard and then always set.

type: custom:power-flow-card-plus
style_card_content: |
  background: lightgrey
entities:

I was trying, but that is not working:

type: custom:power-flow-card-plus
style_card_content: |
        [data-theme="dark"] {background: rgb(100, 200, 100)}
        [data-theme="light"] {background: rgb(200, 400, 200)}  
entities:

How can I change the background dependent on darkmode?
or Can I change that it stays with day mode?
thanks for hep!