Hi all,
i am not sure this will help now. But what i did to update the theme is like this,
1. Under Interface, go to Theme.
2. Right click on the active theme and choose "Open Theme Editor".
3. This will open a modal to updated various parameters for theme (like font style, color, background color, etc) . Among them, you can see "Primary" under Theme Colors field set.
4. When hover over the color, you could get the color picker as last option.
5. Choose your prefered color by picking from pallete, or enter the hex/rgb code.
[V11.14.5]
Thank you.