What I want is when I load my app up it to randomly have a certain colored background from a predefined list of strings stored in a values xml file called colours.
There's a much better answer than the ones provided.
If you want a Truly random color, "randomly" choosing from a res file doesn't prove to be nearly as robust.
Instead, use this code snippet:
Random rnd = new Random();
currentStrokeColor = Color.argb(255, rnd.nextInt(256), rnd.nextInt(256), rnd.nextInt(256));