If you just need a loop toggle button in your Canvas, you can use the “Loop Button” preset. This button allows you to turn the loop on and off and changes color depending on the state of the loop.
If you’d like to change the background of your Canvas to a different color when the loop is active, you can set the Canvas Background to Dynamic and enter the following template:
${osc("/setlist/loopEnabled") ? "amber-900" : "gray"}
Let me know if this helps! 