Minnesotans “of a certain age” will remember roadside billboards with nothing but the words “Don’t Eat the Yellow Snow.” The billboards were a (stealth?) advertising campaign by Rudy Boschwitz’s Plywood Minnesota. It was a long time ago and a Google search does not return any relevant results. But you may want to add blue to the snow colors to avoid eating.
In the late winter when there is usually very little for deer to eat they begin to browse on common buckthorn, a plant they normally avoid. Common buckthorn contains a chemical that is expelled with the urine. The tainted urine is initially yellow or brown but, after exposure to about ten minutes of sunlight, turns bright blue or sky blue.