Style Custom Field Based on Value

Hi,

I was wondering if you fine folk knew how to do this.

I have three custom field in a selector and I can get them out putted and styled on the post no worries. However I would like to give the background of each value output a different colour

So for instance if the value was 1 then the background would be blue
the the value was 2 the background green and so on.

I am unsure how to do this, currently no matter what the value of the custom field they are all styled with the same color background.