My answer is pretty much the same, but I have tried to simplify it.
I am a big believer in the adage that the numbers never lie, so lay colour sampler points on both versions, and move the Info panel into a convenient position. The tray on the right is pure grey, whereas the tray on the left had a touch more red and green than blue. I like to use one curves layer to adjust the hue (which is grey in this case) and another Curves layer to adjust tone.