Thanks for your reply.
This seems to have improved the situation somewhat, as I can now see the red image when I click. However, the original image seems to be overlayed over the top of the red image with a level of transparency. It's almost like the visible: false parameter is changed when the MouseArea is clicked?
It's somewhat hard to explain, hopefully the above makes sense?
If not, I can put together some screenshots to demonstrate the issue?
EDIT: Never mind, it looks like user error after all! I had the z-order configured incorrectly, so the drop shadow was being drawn on top of the image rather than underneath it. Thanks again for your help!