Sequence drag and drop colours

Hello, I'm working in a storyline document a previous colleague built. I'm trying to edit the design of the sequence drag and drop. There are limited things you can do to the design right?
When i select an item to drag it turns light purple. How do you change the colours of a selected item? There is no state on this layer, it doesn't even open up to select individually.

Interested to know if someone can help with this.

Thank you!