Why Black and White Works Best - The Science Behind Monochrome Patterns
Maximum Contrast
White (100% brightness) and black (0%) create the highest possible contrast. Higher contrast means more accurate camera readings under all conditions: dim lighting, distance, angles, dirty surfaces. Black and white isn't aesthetic preference - it's engineering optimization.
What Happens with Color
Cameras judge by brightness, not color. Colors with similar brightness (red and green) are hard to distinguish. Lighting color shifts appearance further. White and black maintain their brightness distinction under any lighting.
Color Vision Diversity
About 5% of Japanese men (1 in 20) have difficulty distinguishing red from green. Globally, 300 million people have some form of color vision diversity. Black and white works identically for everyone because brightness perception is unaffected by color vision characteristics.
Rules for Color Patterns
If you must use color: pair dark with light (navy/white, dark green/white, black/yellow). Avoid similar-brightness pairs (red/green, blue/pink). Always test printed output with a phone scanner - screen colors shift during CMYK printing.
What the reader sees is only light and dark
What the machine reading a QR code sees is not color itself, but only the difference of whether it is light or dark. It sorts the image the camera captured into the two of light and dark with a certain brightness as the boundary, and reads out information from that arrangement. Because white and black are the combination with the largest difference of this light and dark, distinguishing the boundary is easy and scanning is stable. The answer to the question of why it is not colorful lies here. More than the beauty of color, being able to clearly distinguish light and dark is far more important for reading reliably.
What happens when the light-dark difference is small
When you combine light colors with each other, or dark colors with each other, the boundary by which the reader sorts light and dark becomes vague, and scanning tends to fail. For example, placing near-white cells on a yellow background, or black cells on a deep blue background, makes the pattern visible to the human eye but hard for the machine to distinguish. When the state of the lighting or a slight bleed of the print is added, that difference shrinks further. If you want to make it scan reliably, keeping the light-dark difference between background and cells as large as possible is the basic of basics.
Balancing appearance and certainty
The request to want to color a code to match a brand's colors is a natural one. Using color itself is not forbidden, but even in that case, the principle of keeping a sufficient light-dark difference between background and cells does not change. If you choose a dark color for the cells and a light color for the background, and make the difference between the two clear, scanning is maintained even when you add a degree of color. What matters is not to sacrifice the reliable scanning that is its original role by prioritizing appearance too much. After adding decoration, be sure to test on several devices and confirm that the function is maintained.
Screen vs Print Color Shifts
RGB screens and CMYK printing represent colors differently. Contrast sufficient on screen may be insufficient in print. Always scan-test printed color patterns. Black and white eliminates this variable entirely.