Default HDR images look incorrect for different reasons on each platform:
Go the DefaultEngine.ini of EngineTest and set the following:
Then launch EngineTest from the editor for Windows or BuildCookRun -project="EngineTest" -build -cook -stage -pak -package -platform=[Platform]
Image looks correct in SDR
Set r.HDR.EnableHDROutput=1 in console
Either the image will be washed out or completely oversaturated
There's no existing public thread on this issue, so head over to Questions & Answers just mention UE-117299 in the post.