Change Icon color in custom theme

Good day everyone,

I’m wondering where to change e.g. icon colors in the HA custom theme?
I managed to change icon color by adding state-cover-shutter-open-color: "#ffffff" to themes from HACS by editing the corresponding YAML in themes folder. Is this possible for the custom theme?
I really do not like the purple for covers :slight_smile:

All the best and kind regards
Benedikt