Android Material default colors

If you're worried that this color will change over time and you'd like to be up to date if and when Google changes it, you can use ?android:colorBackground.

As of July 2017, it is still #FAFAFA

Finally, I found the solution: #fafafa

It's the Background colour that Google used on the website hakkikonu posted.

Edit:

Maybe it changed over time. Updated answer (thanks to arts777)

https://material.google.com/style/color.html#color-themes link describes all of your question. Also you can see more notes about material design.