It looks like you’re showing the “Critical Path”, which I don’t believe you can customize the coloring. You will need to decide whether showing critical path or different colors is more important. Same applies to the Baselines setting.
If you turn it off/hide in the settings, you will be able to change the “Color by” settings based on what you need/want. Keep in mind the color customization is still limited depending on what setting you use (ie: Group matches the group color you can set, but Board and some others are generated at random and can’t be changed or customized)
As for editing, you can click and drag to change the date. If you need to do more detailed changes, hover over the item in the left pane and click the dropdown arrow > Edit Item
@davide.monticelli See above. I’m thinking you’re in the same boat as OP