Reproduces in 7.1.1 release as well as on SRP master branch (73a37d1858)
Does not reproduce in 7.0.1 or below

Repro steps:
1. Use a project with HDRP or Universal RP
2. Create a PBR shadergraph and open it
3. Create a color node and plug it into emission
4. Set the color to R: 255, G: 100, B: 0, A: 255
5. Set the color mode to HDR, notice that the color changes in the preview
6. Edit the color and change the alpha, notice that the color changes back, even if you set the alpha back to what it was originally
Expected result: the color does not change when switching from default to HDR, or does change but does not change back when you edit the color
Actual result: the color changes, and then changes back when you edit the color again