RicoRock® Acrylic Stains are semi-transparent acrylic stains that are specially formulated to bond to RicoRock precast products and other concrete surfaces. Thousands of artificial rock waterfalls have been colored using these products in the past 10 years. These are waterbased non-toxic stains that instantly give new concrete a weathered rock appearance. No special training or equipment is needed. Rust is an orange-brown color used as an accent. It is usually the first color applied.