As Levi mentioned, you can use coloured QR codes, but you need to ensure that there is sufficient contrast between the two colours. So, using blue and magenta, probably wouldn't work too well. I imagine that if you were to use a light tint with a dark shade, i.e. very light blue and very dark red, then it should be close to the contrast of black and white and work well enough for QR codes. I'm not an expert on any of this, that's just my understanding of it, feel free to correct me Levi!