In dark mode, the green category color and the white text doesn't match

- [x] I am on the [latest](https://github.com/ActivityWatch/activitywatch/releases/latest) ActivityWatch version.
- [x] I have searched the issues of this repo and believe that this is not a duplicate.

- Ubuntu 23.10 :
- 0.12.2:

## Describe the bug

In dark mode, the white text on the green diagrams are impossible to read.

## To Reproduce

1. Enable dark mode in settings.
2. Go to "Activity" when there's a category using the green color

## Expected behavior

The colors for the green category needs to be changed in dark mode. Either the green color, or the text color.

## Documentation


## Additional context