I'm changing the color for a category, in "Data colors" for a barchart.
I copy source color 6-digit code into clipboard.
I open color picker for my category, and select the 6 digits of the current color code with my mouse, from the right of 6th digit, to the left of 1st digit, in order to replace it with my clipboard content.
The color picker disappears.
Observed on septembre and october 2019 releases of Desktop. Same behaviour on service.