The light system gray defined by Apple Guidelines for iOS12 (and used by the default color scheme of the UI controls), is defined as #EFEFF4 (HSB(240,2,96)). It means that the hue is a little bit blue. The new guidelines (iOS13), also use the same Hue/Sat combination but with more variations for the Brightness.
I'll like to learn why Apple designers choose to do that. I imagine that the intention was to change the overall UI tone (like the Glaze painting technique). But I wonder if there is any additional information about that
Why blue? It looks better to the eye or to the iPhone color profile? Or it was a decision to make it look better with space gray color of the iPhone/iPad?