Usage statistic plugin's graph is undistinguishable from the background color of the article page

[Vitaliy-1]

Describe the bug
Described here: https://forum.pkp.sfu.ca/t/immersion-theme-black-on-black-for-the-download-graphs/67457

The background color of the main section of the article landing page is black. Because of the color, the graph of the Usage Statistics Plugin is merged with page's background.

To Reproduce
Steps to reproduce the behavior:

1. Install an activate UsageStats plugin
2. Go to the article landing page
3. See the area with the plugin's canvas

Expected behavior
The graph should be clearly visible.

Screenshots
See the forum