First of all, thank you fot the wonderful grid format - it's awesome!
I have one question, though. I'm confused about the two highlight colours (see the screenshot below)
I know what the first one is - it highlights the current topic section so that the students know what they should be focusing on at the moment.
But - what is the purpose of the second highlighting? What does it do? Why would a teacher (or a student) want/need to highlight/select an image container?