Steps to reproduce:
1. Select a layer
2. Click on background color in properties
3. try to type 3 comma separated numbers for a color
You can't type commas in that field.
Also the numbers vanish, so there is no way to copy colors.
edit: Affects all color entry fields
You can manually enter the color you used on a previous layer, or paste it.
Construct 2 version:
(I think everyone already knows this one, but I'm trying to copy a bunch of colors, and frustrated.)
I suspect the displayed color is replaced by an editable field when clicked on, but the field is number only, so the text is left out. Thus, changing the number field to text should fix the disappearing numbers.