A post on the Autodesk blog for Fusion has announced that, as part of ongoing UI roadmap, the software now offers themes including "dark blue" dark mode. You now have the retina-relieving option to toggle away from Fusion's bright default color scheme between Light Gray, Fusion Classic, and Dark Blue themes, as well as a device-matching selection that intelligently chooses based on your device preferences.
Fusion's classic color scheme will be phased out, but the light grey theme largely preserves its look.