Prior Art
A year ago I made a little widget for visualizing the additive color mixing of RGB triplets. I had been teaching a course on front-end web development, and I wanted a tool to illustrate mixing that was easier to access than the traditional many-chambered Venn diagram.
Just this week I discovered that my widget is identical to the illustrations of painter Charles Hayter in his book A New Practical Treatise on the Three Primitive Colours Assumed as a Perfect System of Rudimentary Information, published in 1826.
See Figure 3 in Figure 1.