Exportet Frame has different color then the video when imported into timeline

Hi,

when I want to mask something unsing an exported frame, the exported frame has a different appearance when I import it and put it in my timeline.

I even tried doing a screen capture and then importing it into Premiere, but it looks the same. Is this a bug or am I sudenly doing something wrong or has something possibly been changed in my settings?

Glad for any help or pointers