For course card images, Canvas chooses colours for colour overlays apparently randomly. Individual users can change the color overlay or turn it off completely; however, it doesn't seem like the module instructor have any control over it.
The instructor should be able to set the default colour for the course's colour overlay - in Settings > Course Details - i.e., in the same place that they can upload a course image. If the instructor has not specified a default colour overlay, then Canvas should pick pick the default colour overlay as it does at the moment. This will enable us to use colour overlays that make sense with out images, use colour coding, etc.
