To reproduce:
1. Open empty project
2. In Project window, create a new Material
3. In Material's Inspector window, try changing Albedo color

Expected: color picker changes the color of corresponding color property field
Actual: color picker doesn't change color and resets to a starting color (check .gif attached)

Reproduced in: 2017.3.0a3
Not reproduced in: 5.4.6f1, 5.5.4p2, 5.6.3f1, 2017.1.0p3, 2017.2.0b6, 2017.3.0a2
Regression starts in: 2017.3.0a3

Note: works with any other color picker
Note: can be fixed by selecting a color picker tool or right-clicking the color property