https://wccftech.com/forza-horizon-3-xbox-one-x-hdr-fix/

Earlier this week, Forza Horizon 3 received the Xbox One X enhancement update which also introduced some HDR issues, making the game look too dark with the feature enabled. It’s now been confirmed that a fix for this issue is coming soon.

The HDR fix has been confirmed on the Forza series official forums. A release date for the fix has yet to be confirmed, but there’s no doubt that we will hear more about the matter soon enough.