Video looks flat on one screen and highly saturated on other screen

[Mikay²]

We work together with external videographers and something seems a bit strange about the exported videos. To my eyes, their videos look a bit too dark for my taste (compared to other videos on youtube) and we had some debates about the saturation of the video.

Sure, this might have to do with different monitors. Also, they use Mac, we use Windows. I just saw a color graded Blackmagic 6K footage that looks quite flat on my screen. But when I watched in on my TV, it look way better. Now I wonder what's the problem here because, as said, other videos look fine on my notebook. They set their exports and sequences to Rec.709. So I am not really sure what the issue could be.

Is there some other data in the exported videos that determine how monitors display the videos? 

[John V Knowles]

This is a WHOLE discussion about how color is viewed and managed. In short, it will NEVER look the same on two different monitors. This is what Colorists struggle with all the time. The best option is to have a calibrated system and a monitor you know you can trust to be accurate to your footage and color grade. This usually involves a separate video card that bypasses your GPU (like Blackmagic or AJA) and a calibrated monitor (not cheap). And even then, the output from this system would still look diffrerent on YouTube in Edge on a cheap PC. 

[Carlos Ziade]

check and try color management settings:

https://helpx.adobe.com/premiere-pro/using/color-management.html

Youtube and social media platforms usually have their own color management,

so as John said, I don't think you will get the same coloring results on different platforms

and this is really a challenge and needs thorough understanding of color grading 

@R Neil Haugen