Operating system: Debian 10
Graphics card: geforce 970

Broken: 2.81 alpha, a571ff2c16c6 (from checkout last week)
Worked: Unsure.

A color effect strip, with Offset or Crop enabled, will not update the Preview color when the color is changed.

Reproduce:

1. New -> Video Editing
2. Add -> Color
3. Set color -- one that represents your true identity.
4. Enable Crop
5. Set color to something beautiful... but not the color that represents your identity. Sorry, but it must be a distinguishable color. (The beauty of it is optional.)
6. Strip itself's color will show the new color, but the VSE Preview will not.

That's sufficient, but to see more:

6. Hit left once and right twice, to change back and forth in the timeline, and you will see the original frame was not updated in the preview, but either side receives the new color.