Page header background color isn't updated in real time when editing a newly created Color Theme

steps to reproduce:

• login
• create a new color theme
• change the color of "Page header background color".

You will see it will not update in real time.

Please note that header image field is empty, so there is no image in front of the color.

Saving the Page will take account the modification.
Only issue is that the color doesn't change in real time

Image attached