Chameleon Pens: One Pen Blends Multiple Color Tones by Chameleon Art Products — Kickstarter
Chameleon Art Products, 15 Pens + 10 Color Tops (25-Pen Deluxe Set) - Walmart.com
British Chameleon Pens, Gradient Marker, Watercolor Marker, Special Marker For Painting, Suitable For Students And Beginners - Art Markers - AliExpress
Chameleon Pens are Alcohol Markers that let you "Color like no other"