MTN Water Based Marker - 3mm - RV30 Prussian Blue is a great water based thin line graffiti marker or fine art marker with a high coverage paint that works well for fine detail work. Similar to a Molotow one4all this 3mm paint marker is perfect on canvas or any graffiti art project. Montana Colors Water Based 3mm Paint Marker RV30 Prussian Blue is a full middle blue hue paint refill.