What Is ΔE94 (Delta E)? Color Difference Explained

When two colors look "almost the same" or "clearly different," how do we put a number on that? Designers, printers, and color scientists use a metric called delta E (ΔE). One of the most widely used variants is ΔE94—and it's the same formula Color Guesser uses to score your guesses. Here's how it works.

The Problem With RGB Distance

You might think measuring color difference is simple: just compute the Euclidean distance between two RGB values. But RGB treats red, green, and blue equally, while human vision doesn't. Two colors with the same RGB distance can look very different in perceived difference—or vice versa. We need a color space that better matches human perception.

CIE Lab and Perceptual Color Space

CIE Lab (or CIELAB) is a color space designed to be perceptually uniform. In Lab, L is lightness (0 = black, 100 = white), a is the green–red axis, and b is the blue–yellow axis. Distances in Lab space correspond more closely to how we actually see color differences. That's why ΔE formulas are built on Lab, not RGB.

How ΔE94 Works

ΔE94 refines the earlier ΔE76 formula by adding weighting factors for chroma and hue. In practice: a ΔE94 value of 0 means identical colors; 1 or less is typically not noticeable to the human eye; 2–3 is a subtle difference; and above 3 is a clearly visible difference. This makes ΔE94 a reliable standard for design, printing, and quality control.

Why Color Guesser Uses ΔE94

Color Guesser compares your selected swatch to the target color in CIE Lab space and computes ΔE94. We then convert that perceptual distance into a 0–100 score per round—so a perfect match scores 100, and the score drops smoothly as the colors diverge. This gives you fair, intuitive feedback that reflects how well your choice matches what the human eye sees.

Other Delta E Variants

ΔE76 is the simpler Lab-based formula; ΔE2000 (CIEDE2000) is a newer, more complex standard that improves accuracy in certain regions of color space. Color Guesser uses ΔE94 as a balance of accuracy and computational simplicity—it's well-established and works great for our use case.

Conclusion

ΔE94 is the industry-standard way to measure color difference in a way that matches human perception. Understanding it helps you interpret Color Guesser's scoring—and gives you a deeper appreciation for how we quantify the subtle art of color.