Feature Focus: After Effects respects Dark Mode on macOS
As of the After Effects Beta24.6x35 update, we are including support for macOS Dark Mode, as well as some performance improvements on macOS.

This means that not only will all After Effects dialogs will have appearance-appropriate Title Bar coloring, but system windows like File Import will render with the correct appearance for your current system setting. After Effects appearance theme coloring is not tied to System Appearance, so you can have a light AE with a dark macOS, if you so want.
We have seen occasional rendering-only issues in custom button UI in the Effects Controls Panel that don't affect functionality. We've reached out to the developers of those plug-ins but as Beta Testers, please let us know if you observe any unwanted UI rendering differences in new beta builds, particularly with third-party plug-ins. If you are a developer, please test your software with this new release, particularly if there is any custom rendering.

