You may often wonder whether QR codes should be black and white only. It would be pertinent to mention here that emphasis should be laid on a good contrast between the dark and light pixels or modules. Moreover, a colored QR code should not have any negative aspect pertaining to the color scheme.
The site https://www.oysso.com would lay emphasis on the dark modules being slightly darker than the usually white modules, especially when it is in color, lest it may confuse several QR code readers. You would be able to create colored QR codes with Oysso free of charge. Simply choose the background or the front color.