Hi, Calum,
Unfortunately, there's no way to disable or edit the Correct and Incorrect banners that appear during a review.
If you want to use the review function but don't want those banners to show, just hide that part of the slide with a shape on the Review layer.
- If you don't already have a Review layer, you can add one with that name, and Storyline will (probably) show it during a review. Or, to ensure functionality, have SL add the layer. It'll do that when you enter any text in the "Post-quiz review" field at the bottom of Form View.