Is it true that Canon sensors have half the number of colors than Nikon, Fujifilm or Sony sensors? I read this on Quora.
It is not true as a general statement.
The statement seems to be a confusion as to how Canon's "dual pixel autofocus" works (a feature of most modern Canon DSLR's)... The dual pixel phase detection autofocus system combines two sensor photodiodes (sensor/AF "pixels") as a single image pixel; thereby reducing the potential color separation/sensitivity by half compared to if the sensor photodiodes were filtered/recorded separately.
The (potential) issue/misunderstanding here is due to Canon's use of common terminology and calling sensor photosites/photodiodes pixels... which isn't really the case.
It might be true in comparing two specific cameras where the Canon is recording images at a lower bit depth (e.g. only records jpegs), or the Canon has lower color sensitivity at a given ISO. But that is also dependent on the specific cameras being compared. I.e. the Canon 7D is ~ 1-2 bit lower than the Nikon D800 at any ISO; but the 5D Mk4 is pretty much equal to the D800 at all ISO's (each bit is 2x, but 2 bit here is less than 1 bit/color).