Figure 2 shows the measured Color Gamuts in Ambient Light for the Apple Watch and Apple Watch Sport along with the Standard sRGB / Rec.709 Color Gamut in black. The outermost white curve is the limits of human color vision - the horseshoe is the pure spectral colors and the diagonal is the Line of Purples.
Note that the Color Gamut decrease with increasing ambient light is larger with Sapphire than with Glass due to its higher Reflectance. These measurements were made with the displays forced to Maximum Brightness by fooling the Ambient Light Sensor. With the the Ambinet Light Sensor operating the display Brightness would be lower and the Color Gamut decreases with ambient light even larger.
Figure 2b. Apple Watch Sport with Glass in Ambient Light