The Color Checker is a painter's tool to facilitate the process of reproducing a color from the real world using paint.

I've simply turned this design into a 3D printable format. Original design is by Mark Carder aka Draw Mix Paint:
https://www.youtube.com/channel/UCXgSi1Kwt7K2RUOapq2KHuQ
http://www.drawmixpaint.com

This video describes how to use the Color Checker:
https://www.youtube.com/watch?v=TuZ0t5FR9f0

Printing:

For best result PRINT COLOR CHECKER LAYING DOWN. If printed standing up the skinny bar holding up the viewing ring is very weak and easy to break. However if printed laying down it is still a bit weak but much much stronger.

If I get around to it I'll create a v2 of the Color Checker with a stronger ring holding part (maybe as a 2nd piece that snaps on) as well as a slightly smaller view ring radius.