Surprise someone special by decorating their car with this Royal Blue window marker. This special Blue paint marker can write on car windows and other glass surfaces with ease. It's great for proposals and other surprises. Decorate a car Before driving to a sporting competition or high school graduation ceremony To make things more exciting. Or, create a design to go on a sliding glass door for a 4th of July party. After the festivities are over, this Blue car window marker wipes away with water for a sweet and simple cleanup.