The problem with most color theory education is that it treats color as an abstract system to be memorized. You learn that red and blue make purple, that complementary colors sit opposite each other on a wheel, that warm and cool tones have psychological effects. You memorize it. Then you sit down to design something and you still can't make colors work.
This site takes a different approach. It gives you a target color — usually a specific hue and saturation and lightness — and asks you to mix it from a limited palette. No explanation first. You just try. You fail. You try again. The interface gives you immediate, unambiguous feedback about whether you're getting closer.
After a few rounds of this, something clicks. Not an abstract understanding, but a practical one. You develop an intuition for how hue, saturation, and lightness actually interact — because you've spent twenty minutes trying to hit targets and missing them in specific, instructive ways.
What it actually covers
The site works through a progression of concepts: hue mixing, saturation control, the relationship between lightness and perceived warmth, complementary contrast, and — this is the clever part — the difference between what colors are and what colors look like next to each other. That last one, simultaneous contrast, is notoriously hard to explain with words. Here you feel it.
There's also a module on color naming that is quietly devastating to anyone who thought they knew what "teal" meant. Turns out there are several valid definitions and they're not quite the same color.
Who made it
The credits page attributes it to an independent developer in Seoul who was frustrated teaching themselves color theory from textbooks. That origin story shows in the design — the site is practical to the point of being almost austere. No brand identity, no explanatory copy, minimal navigation. Just the exercises and the feedback loop.
It has apparently been running continuously since 2021, which is longer than most side projects of this type survive. The exercises have been updated a few times but the core interaction has stayed the same. That suggests the developer still considers it unfinished or at least improvable, which is probably correct — the section on color in typography feels rushed compared to the rest.
For anyone who has ever felt vaguely defeated by color and wants to actually fix that, this is the right starting point.