Hello guys That is the question I ask myself. Xiaomi he uses different types of screens for xiaomi MI4? in November 2014, I bought my first MI4 64GB wcdma for my wife. this mi4 has a perfect screen with bright white, very bright and contrast. In April 2015, I bought a black 16gb MI4 wcdma that has a screen with a white that pulls yellow, not bright, not a lot of contrast, a different screen from the first MI4 made in October 2014. I still buy a third Mi4 FDD LTE 4G 16GB white with a screen having the same rendering as the black mi4. There are some days I buy a third MI4 wcdma 16gb black screen with a worse than any other, a yellowish screen. I conclude that the MI4 do not have the same screens. Have you noticed this problem?