Robin makes a good point here about using dark mode thinking as a way to uncover any assumptions you might have unwittingly baked into your design:
Given its recent popularity, you might believe dark mode is a fad. But from a design perspective, dark mode is exceptionally useful. That’s because a big part of design is about building relationships between colors. And so implementing dark mode essentially forced everyone on the team to think long, hard, and consistently about our front-end design components. In short, dark mode helped our design system not only look good, but make sense.
So even if you don’t actually implement dark mode, acting as though it’s there will give you a solid base to build in.
I did something similar with the back end of Huffduffer and The Session—from day one, I built them as though the interface would be available in multiple languages. I never implemented multi-language support, but just the awareness of it saved me from baking in any shortcuts or assumptions, and enforced a good model/view/controller separation.
For most front-end codebases, the design of your color system shows you where your radioactive styles are. It shows you how things are tied together, and what depends on what.