button01.setBackgroundColor(getResources().getColor(R.color.red));
color.xml
colors.xml
<?xml version="1.0" encoding="UTF-8"?>
<resources>
<color name="red">#f00</color>
<color name="green">#0f0</color>
<color name="blue">#00f</color>
<color name="black">#000</color>
</resources>