Colorpik Pen : Copy And Draw With 16 Million Colors by COLORPIK — Kickstarter
Marvy Color In Markers
Posca 16-Color Paint Marker Set PC-3M Fine
Two-color markers, 16 Kidea colors
Shuttle Art 51 Colors Dual Tip Alcohol Based Art Markers, 50 Colors plus 1 Blender Permanent Marker Pens Highlighters with Case Perfect for Illustration Adult Coloring Sketching and Card Making
The Many Benefits of Coloring with Crayons - The OT Toolbox
Brush Pens: The Definitive Guide - Jackson's Art Blog
Double-sided felt-tip pens Staedtler 72k Design Journey No. 3200
Prismacolor Chisel & Fine Markers
Sharpie S-Note Duo Dual-Ended Creative Markers