Resist art is a fun technique where color is repelled from design areas that have been printed with this coating. It’s easy and fun to create beautiful, frame-worthy art by simply brushing watercolor paints over the surface of the sheet.

https://www.ssww.com/item/watercolor-...
https://www.ssww.com/art-supplies-and...

Water-based markers or watercolor pencils can also be used to color the poster. Brush the image with water to allow the colors to blend and create subtle shading.