These are definitely theme variables, not card options, so it needs to go in your themes configuration, either in your configuration.yaml or in a separate themes yaml, depending on how you have structured that.
Once you define a theme, remember you need restart or call frontend.reload_themes, and then select that theme from your user profile page.
I was after the theme method. It appears I canât override default theme but have to create a custom theme just for energy dashboard⌠Is that right ?
Yes if you want to change colors of things via theme variables, you need to create a theme, and you have to select that theme instead of the default theme.