You can use this to call predefined android colours:
element.setBackgroundColor(android.R.color.red);
If you want to use one of your own custom colours, you can add your custom colour to strings.xml and then use the below to call it.
element.setBackgroundColor(R.color.mycolour);
However if you want to set the colour in your layout.xml you can modify and add the below to any element that accepts it.
android:background="#FFFFFF"