I am just a newbie to smart home and try to learn and build it with my own hands. Thanks for your advice and help!
With some great guys’ suggestion, I just bought a bunch of Liner WD500Z-1 wall switches and try to install it but found on my current wall switch it only has three wires - Black, White and bare copper-ground wire which I think is the most common wires in a residential house. But on Liner it has Black, White, Green-ground, and Blue. I know color to color wiring, but what to do with the blue wire?
The Liner installation video says the Blue wire connects to the load,
Call an electrician. No, seriously, wiring is not the place to learn as you go.
If you live near a Home Depot, they may offer classes on how to install a light switch or a GFCI receptacle that are a good place to start and learn the tools and safety tips you’ll need for even simple electrical projects.
p.s. A friend of mine who is an electrician says, “Color just tells you which wire to test first.” There’s no guarantee the color you see means what you think it means, even if professionally installed.
look inside the light switch box. If there is no other wire back there then your power source is at the light fixture box. I am an electrician but can’t guarantee a good one