Why are QR Codes White and Black?

 Black and white are the standard colors for QR codes since they have the maximum contrast.

The more starkly the background and data modules differ in color, the easier it is for phone cameras and QR code scanners to read each code.

Further, when colors were less contrasted, it was difficult and inaccurate to read QR codes in the past. 

The technology in your smartphone's camera used to have trouble registering those unique data points on a code due to poorly chosen color patterns, which prevented it from being detected swiftly or at all. 

A black-and-white QR code is easy to scan

See more: https://barcodelive.org/do-qr-codes-have-to-be-black-and-white-detailed-explanation