Use Sunscreen Bag Tag

thingiverse

Printed tag in UV color change PLA shines bright with vibrant hues. White lettering on the tag pops out boldly against the colorful backdrop. To fit perfectly onto kids' backpack straps, the tags were carefully scaled down in size. As sunlight hits the tag, the colors shift dramatically, turning a rich purple tone that stands out remarkably against its surroundings. When shaded, the tag's background seamlessly reverts to a crisp white, allowing the lettering to shine with clarity.