Why does sampling onscreen colors result in (slightly) wrong colors?

Can someone please explain to me why this happens. I'm sure it has something to do with color spaces / settings which are the bane of my existence. 

In Premiere Pro (Windows 10, Premiere 2020 V 2..3.0) I want to make a COLOR MATTE that matches a color in my imported video. 

This video may be a MOV file exported from Animate, or an MP4 file provided by clients, etc. etc. 

I create a new Color Matte, set the size etc. When the Color Picker dialog appears, I use the eyedropper to sample the color from the area of the video I want to match.

Premiere creates a Color Matte. But, when I place this color matte on top of my original video, the matte doesn't match the underlying color. It's *close* but slightly off. 

For example, the color of the original video is #CDCFC4. The Color Matte *says* it is #CDCFC4.  *BUT* the new color matte displays onscreen as #CACCD2. 

The color of the original video is #EA7100. The Color Matte *says* it is #EA7100.  *BUT* the new color matte displays onscreen as #E96900.  

Even the color picker in Premiere identifies the color as #E96900 while the Color Matte continues to insist that it is set to #EA7100.

What gives?