A couple of years ago, I fell in love with a color scheme: off-white text accented with a buttery yellow-orange and a neutral blue against a deep gray, the "color of television, tuned to a dead channel," to borrow a phrase from Neuromancer author William Gibson. The colors were part of a theme called Solarized Dark for the popular MacOS code editor TextMate. To be honest, I didn't think much of Solarized at first. But I soon found that I couldn't work with any other color scheme. Staring at screens all day can make you particular about fonts and colors.

It turns out I'm not alone. I'm not a coder by trade, but I like to use code editors for writing and organizing notes. While hunting for tools after switching from a Mac to Windows, I started to see Solarized Dark and its sibling Solarized Light, which uses the same 16-color palette, practically everywhere I looked. It's hard to say how many programmers use it. The design is free and open source, so there’s no tally of purchases. It’s available for every major code editor and many other programming tools. Microsoft even bundled it with its popular code editor VS Code. Solarized has a loyal following.

"If I bring up a terminal window that doesn't have Solarized, I feel out of place; I don't feel at home," says Zachery Bir, a Richmond, Virginia, programmer and artist who has been using Solarized since shortly after it was released in 2011. Bir likes Solarized so much he uses it as the color scheme for his computer-generated art. "I didn't trust myself to come up with a palette that was balanced and looked good both in a dark and light medium," he says.

The Solarized color scheme is no accident. It reflects the obsessive attention to detail of its creator, Ethan Schoonover. "I didn't release it until I was 1,000 percent sure I loved all the colors and they were all dialed in mathematically," Schoonover says. "I had multiple monitors, some were color calibrated, others were deliberately messed up. Sometimes I showed my wife, who thought I was a little nuts."

Too Much Contrast

Schoonover was working as a designer and programmer in Seattle when he started work on Solarized in 2010. He'd recently switched operating systems and was disappointed in the color schemes available for the tools he used. Many applications offered only a simple white-on-black scheme that harkened back to old-school text-based computer terminals. But Schoonover found these throwback color schemes much harsher than the retro displays they tried to emulate. That’s because the backgrounds displayed on old 1980s monitors weren't truly black, Schoonover says. "They had less contrast." Today’s LCD’s, on the other hand, are capable of displaying much darker, and much brighter, colors.

The optimal amount of contrast for text on a screen is controversial; many people prefer high-contrast themes. But contrast wasn't Schoonover's only concern. He found most low-contrast color schemes lacking as well. Even the best-designed themes tended to use at least one color that appeared distractingly brighter than others. That's because the apparent brightness of a color varies depending on its background. In other words, a specific shade of blue will appear more or less bright, depending on the surrounding colors.

This phenomenon, known as the Helmholtz–Kohlrausch effect, is particularly aggravating for programmers because coding tools use color to distinguish different parts of code. In the code for a web page in a typical text editor using the Solarized Dark theme, for example, web links appear in green; the syntax for formatting, such as adding italics, is blue, and comments that developers write for themselves are gray. Ideally, the colors should help tell these elements apart, but no single element should stand out more than others.