Hi Jamie,
I would just hold a global "flag" (variable) and switch it on/off when used/unused.
Although, this might need to be injected into the application's js file, to be in the global scope and not a specific widget.
A cleaner solution would be to create a Dojo module - a separate class, which will hold that flag. Load that module as part of the application and display the color based on the flag.
Another idea would be to use Dojo topic module - publish and subscribe to change the color when needed - https://dojotoolkit.org/reference-guide/1.10/dojo/topic.html
there many ways of doing this
Shay.
Shay