For symbol instances there is this neat override UI for colours. I’d like this for any selection or groups. Right now if the same colour is used in text, border and fill, I have to change each one at a time. This is annoying when exploring colour palettes.
Stretch goal: allow dragging a colour swatch onto another to swap colours.
Hi Gael and welcome to the Sketch Forum! It’s great to have you here and thank you for sharing this insight with us!
I can totally see the benefits of this improvement! It’d be much faster to make changes and explore color variations or palettes like you mention. I like the stretch interaction of drag to swap too!
I’ve documented this as a Feature Request and shared it with the team 
Welcome again and please let us know of any other feedback you have