Apple Watch Space Grey Aluminum Has Gotten Darker Starting With The Series 4
Apple seems to change the hue of their colours after a few generations. Witness the current iPhone 12 in the product(RED) colour, which is noticeably more orange than previous product(RED) versions of the iPhone XR and 11.
We also see that the Series 4-6 Space Grey aluminum is darker than Series 0-3, as you can see by these photos:
Currently, most of our grey aluminum bands (Ligero, Velo, Qrono and Vitero) are colour-tuned to the Series 0-3 so far, and will be a lighter shade against the darker grey colour.
The exceptions would be the 42/44mm Vitero Ruby Grey and 42/44mm Vitero Azur, which are colour-matched to the darker Series 4-6.