Black when it's empty.
It reveals the secret of your health when it contain a hot beverage 

• Ceramic
• Black matte finish when cold
• Reveals the print when exposed to hot liquids
• Dimensions: height - 3.85" (9.8 cm), diameter - 3.35" (8.5 cm)
• Made in China. Printed in the USA and EU

Note that in some instances the coating might not be 100% opaque and an outline of the design might peek through a little. Also, you shouldn't put the mugs in a microwave or dishwasher since it can damage the coating.