How to add an Opacity selector to the color picker in Theme Settings

Store Design
1

Hi,

I’m new to liquid, so I’m having trouble adding an opacity selector to the color picker UI. Currently, mine looks like this:

Alpha value of colors can't be selected
Alpha value of colors can't be selected318×678 29.3 KB

I would like to select opacity levels for the background colors. The theme I’m using is “Express”.

I’ve found this thread but I can’t work it out changing the liquid code (I actually don’t even know if I’m editing the right file).

Any insight?

Thank you