We are seeing an issue in the "Roadmap Timeline" report where horizontal bars with display color mapping of "Navy" (from the Modern UX -> Roadmaps section), do not get displayed properly. A sample screenshot of the issue is as below.
This has been observed to be an issue in version 15.9.3 of the application, that is not reproducible in version 16.0.0. The report in v16.0.0 renders the colors correctly. You can export the Roadmap Timeline report from a v16.0.0 system, and import it into v15.9.3.