A colour picking widget would be amazing.
that's already included, you can use the predefined action "show color picker" which will open the native macOS color picker. If you are a developer I recommend to additionally install the panic developer color picker addon for the system picker.
//edit : ah sorry, just realized you probably want one included in the Touch Bar . Yeah that might be a good addition.
Yes, a color picker included in the Touch Bar would be great. The one for photoshop is very helpful.
I would absolutely add a Color Picker menu bar item/widget group to my preset immediately for such a feature. I use apps like ColorSnapper constantly, so this would be a big productivity feature for me. And I bet I could bake in 90% of ColorSnapper's functionality into the Touch Bar if I had the tools to show a color picker on the Touch Bar, a button to copy the current color being displayed on the picker, and history of last colors copied. Would also be useful to be able to make a button that launches a magnifier loupe to capture a color from anywhere onscreen.