I just bought a 13" model today to compare it with my 15". However, the screen of the 13" seems a bit more yellowish than the 15". I did the calibration, but it is still not as white as the 15". Is it defective ?
Open system preferences. click of Display, click on Color, click on Calibrate, click on Continue, uncheck "use native white point" then move the slider to the right until the whiteness of your new MacBook matches that of your other MacBook.