Colour and Image Quality
Do we have anything better to go on other than the reviewer's subjective judgement?
Perhaps some colourimeter tests perhaps, I'm genuinely interested.
I reviewed Sharp’s first Quattron TV last year, and although it was rather pricey I was impressed by the image quality that it provided thanks to its innovative addition of a fourth yellow pixel to the standard mix of red, green and blue. Sharp Quattron LC-40LE831E Jaundiced view? Sharp's Quattron LC-40LE831E screen features …
The entire broadcast system is set up to deliver a standardized signal to a television reproducing a specific colour space (Rec 709). This colour space can be completely covered using only red blue and green pixels. A Quattron system has to invent a signal to give the yellow pixels something to do, and in the process displays colours that were never there in the original broadcast.
I'm guessing you can figure out how well that works in colourimeter testing.