Public beta testers can deploy the latest beta of Sierra over the air via the Software Update mechanism provided they have installed an appropriate configuration profile through Apple’s Beta Software Program website.
macOS Sierra 10.12.4 beta 2 for public beta testers includes the same features as the first developer-only beta which released on January 24.
Like on iOS, where Night Shift allows you to adjust the temperature of the display from cool to warm based on the time of day, Night Shift Mode in macOS Sierra gradually shifts your Mac’s display from blue to yellow.
This cuts down on exposure to blue light, which is believed to cause sleeping problems. You can access Night Shift Mode on your Mac in System Preferences, Notification Center or through Siri.
Apple also released iOS 10.3 beta 2 to public testers two days ago.
If you’re signed on Apple’s public beta program and have installed a configuration profile on your device, you can install a beta of iOS 10.3 over the air in Settings → General → Software Update.