Few weeks ago, an update for Forza Horizon 3 for the Xbox One X caused some problems with HDR exposure. The problem basically causes the screen to appear as being either too bright or too dark. Now, the issue has been identified and a new patch has been released to fix the problem.
The Xbox One X update brought a number of enhancements for the game including support for native 4K resolution and a number of other visual upgrades such as increased shadow resolution, improved visual effects, and more. It was unfortunate that the update caused such a problem but Turn 10 quickly acknowledged the problem and promised the community that they would soon release a fix.
The problem has been identified and was supposedly caused by improper exposure calculation in some situations. The new patch is now available to download and should help you to get back to racing without any problems. Forza Horizon 3 is now available for Xbox One and PC.