I couldn’t really find an answer above yet to your question where the actually css can be found or how you can overwrite / add a style. Here is what you can do:
- AFAIK the CSS file that is used is in /usr/lib/node_modules/frontail/web/assets/styles but you should only use that for reference and not really edit it.
- if you want to add css or overwrite css, I would recommend to read the following document which I found in the openhab habpanel github project: https://github.com/pmpkk/openhab-habpanel-theme-matrix
- Basically what you have to do is
** create a sub folder (eg. myfolder) in /etc/openhab2/html/myfolder
** add a css file mycss.css to the folder and add your styles
** then in the habpanel ui go to the settings on the left and click the cog wheel on the bottom
** Look for the setting "additional stylesheet (optional) and add the file path /static/myfolder/mycss.css
Hope that works for all who want to modify and optimize the css.