Setting RGB values in a material's color field (such as Albedo color in a material using the Standard shader) to 1 (e.g. R=1, G=1, B=1) causes each color channel that was set to 1 to report its value as 191. After that point, the values cannot be changed, even after new values are typed into the color panel. The alpha channel doesn't seem to be affected by this issue.

To reproduce:

1. Download attached project "ColorBugTester.zip" and open in Unity
2. In Project, window press Create > Material
3. Click on the Albedo color to open the Color panel
4. Set the R, G and B channels to 1
5. Close the Color panel
6. Reopen the Color panel by clicking the Albedo color again

Expected result: RGB channels still report that their value is 1
Actual result: RGB channels all now report that their value is 191

Notes:
- This issue reproduces on both Windows and OSX
- If you try to change those values, close and re-open the Color panel for the Albedo color you will see that they still report their values as 191

Reproduced on Unity 2018.1.0a6, 2018.1.7f1, 2018.2.0f1 and 2018.3.0a3
Not reproduced on Unity 2017.4.6f1 and 2018.1.0a5
Regression on Unity 2018.1.0a6