December 11, 2023 Amy Shulke Ohuhu Marker, Ohuhu Swatch, Ohuhu Test PB3 Cobalt Blue: Testing Ohuhu Markers for Lightfastness and Quality December 11, 2023 Amy Shulke Ohuhu Marker, Ohuhu Swatch, Ohuhu Test PB3 Cobalt BlueLet’s take a closer look at this Ohuhu Marker and its ink characteristics.