{"id":1,"date":"2024-04-07T08:10:12","date_gmt":"2024-04-07T08:10:12","guid":{"rendered":"http:\/\/csholgate.com\/?p=1"},"modified":"2024-06-18T22:40:15","modified_gmt":"2024-06-19T05:40:15","slug":"colors","status":"publish","type":"post","link":"https:\/\/csholgate.com\/index.php\/2024\/04\/07\/colors\/","title":{"rendered":"colors"},"content":{"rendered":"\n

Recently, I have been falling in love with and haunted by colors. I believe color choice in figures is an under appreciated but critical for communication of data and ideas. Colors should be good looking, accessible (including printing in greyscale well), and reflect the underlying data. In trying to understand color better, I have fallen into a deep rabbit hole of color theory. I won\u2019t pretend to be an expert here, but I have learned things along the way that are hopefully interesting if not helpful for how scientists can choose better colors.<\/p>\n\n\n\n

It isn\u2019t as simple as primary colors.<\/h2>\n\n\n\n

Having no serious art training, I don\u2019t think my brain ever internalized what the primary colors are. If you would have asked me, I probably would say red, green, and blue (RGB) based off my love of technology and the RGB pixels that power displays. These three colors when added together can produce many of the colors the human eye can see! But still not that<\/em> much\u2014think around 30\u201350% depending on the exact technology used.<\/p>\n\n\n\n

If I did have art training, I\u2019d probably say that red, yellow, and blue (RYB) are the primary colors. These are called the \u201csubtractive\u201d colors because they subtract from a white background. Adding the three primary colors together creates black. Ask a printer and they\u2019ll have a similar but slightly different answer\u2014cyan, magenta, yellow, and possibly black (CMYK). <\/p>\n\n\n\n

Regardless of what the primary colors are, in principle these primary colors can combine to create a whole color wheel. But color wheels produced from different primary colors are distinctly different. For example, in RGB space, red and green are \u201cbuddy\u201d colors; they can be combined to produce yellow as a new color. In RYB color space, however, green is created through the mixture of yellow and blue and, as such, is directly opposite to red on the color wheel. In other words, this suggests that red and green can not<\/em> be mixed to produce a new color. This also sort of follows intuitively\u2014it is easy to think about a color that is a reddish-yellow, but I cannot picture in my head what a reddish-green would be other than a muddy blah<\/em>. <\/p>\n\n\n\n

This thinking motivates other, more niche, sets of primary colors. Opponent process<\/a> (a color theory) and CIELAB<\/a> (a color space like RGB), as two examples, describe four \u201cprimary\u201d colors, each setup as an opposite pair: red and green, and blue and yellow.1<\/a><\/sup> This allows for any color to be described through a combination of lightness, and of hues in the red-green and yellow-blue axes. <\/p>\n\n\n\n

Defining color is just math.<\/h2>\n\n\n\n

All of this boils down to a key point: working with colors requires creating a color space<\/em> and a way to access it through mathematics. That\u2019s really all that RGB, CMYK, or CIELAB models are. When choosing a color, say in Adobe Illustrator, this is most commonly done through setting values for one of four different systems:<\/p>\n\n\n\n