There were Bayer sensors before Red. If I remember correctly, three-chip cameras became impractical at higher resolutions because of the focusing problems that

There were Bayer sensors before Red. If I remember correctly, three-chip cameras became impractical at higher resolutions because of the focusing problems that resulted from refraction. Red, green, and blue wavelengths refract at different rates... which was a problem when they're all coming through the same lens. I don't remember details beyond that.