Änderung der Farbe nach Export

There are a couple different things to be aware of.

First, you need to learn how to set & control the many color management options to your needs. All now found in the Color Workspace/Lumetri panel, the tab named Settings. 

Most users should have Display Color Management on, and Mac users should also check Extended Dynamic Range. Auto-detect Log and auto-tonemapping are interactive, and both should be on for most workflows.

Sequences have color spaces now, and the export preset used must match the color space of the sequence. ONLY use presets with HLG or PQ in the preset name if the sequence has that same HDR format as the color space.

The "proper" Viewer/display gamma for Rec.709 is 2.4 for 'darkened room' working, 2.2 for bright room surroundings.

Second, ... for Mac users, there's a pick your poison option. Gamma 1.96 QuickTime will more closely match inside Premiere to outside Premiere in QuickTime Player and Chrome and Safari browsers ... but only on Macs without Reference modes!

All other screens will see a darker image. Sorry, but thanks to Apple, that's Life.

Try turning off Hardware encoding in the Video tab of the export settings.

If you bring the exported file into Premiere Pro, does it look OK?

What are your media properties, sequence settings, and export settings?