A practical contrast checklist for coloured, white, and inverted QR codes: module vs background, paper finish, lighting tests, and when to flip back to dark-on-light.

Most “pretty” QR failures are contrast failures. Use this checklist before you commit to a print run — then generate a proof with the coloured or white/inverted tools.

1. Module vs background

Modules clearly darker than the background (or clearly lighter for a true invert)
No pastel-on-pastel or yellow-on-white
Finder squares still obvious when you squint

2. Paper and finish

Prefer matte for inverted and dark venue lighting — see matte vs glossy
Avoid varnish hotspots over the matrix
Leave a quiet zone (margin) around the code

3. Device proof

Scan on iPhone Camera and at least one Android
Test in the real venue light (not only desk lamps)
Compare against a known-good black-and-white control

4. When to abort a fancy colour

If any phone fails twice, flip to dark modules on light stock and brand the frame instead. Reliability beats a palette that only works on your MacBook.

QR code contrast checklist before you print

1. Module vs background

2. Paper and finish

3. Device proof

4. When to abort a fancy colour