Repro:
01 - Create a new Unity project using either of the above builds.
02 - Create a new material from the project view.
03 - Enable emission for that material.
04 - Click the colour picker swatch to bring up the picker window
05 - Select a pure red colour using the centre HSL square. Keep the intensity value at 0.
06 - Close the picker window and reopen.
07 - Observe that the intensity remains at 0.
08 - Now increase the intensity to 1.
09 - Close the picker window and reopen.
10 - The intensity value will have changed. Now it reads 1.416925 (wrong)

Reproducible in : 2019.1.0a7, 2018.2.10f1