infos on a theme with white background for the boxes are not readable

[arbor95]

Describe the bug infos on white background are not readable

To Reproduce Steps to reproduce the behavior:

1. Go to 'https://wijzijnfamilie.nl/tree/wijzijnfamilie'
2. Click on 'Theme Color palette', select "Justblack"
3. Click "charts"... to see your fanchart
4. See error: The info within the white boxes (circle segments)

Expected behavior Info should be readable (dark/black on white)

Screenshots If applicable, add screenshots to help explain your problem.

Desktop (please complete the following information):

• Browser [e.g. chrome, safari] : Chrome
• Webtrees version [e.g. 2.0.12] 2.1.18
• Version of fan chart [e.g. 2.2.1] 2.6.2 (at freris.de)

Additional context I created an issue for the same behaviour at github for JustCarmens JustLight/JustBlack theme. I do not know where to solve the issue.