[android] How to change background color in android app

You can use simple color resources, specified usually inside

res/values/colors.xml.

use

<color name="red">#ffff0000</color>

and use this via android:background="@color/red". This color can be used anywhere else too, e.g. as a text color. Reference it in XML the same way, or get it in code via

getResources().getColor(R.color.red).

You can also use any drawable resource as a background, use android:background="@drawable/mydrawable" for this (that means 9patch drawables, normal bitmaps, shape drawables, ..).