To do a good job of it your looking at the price of a new case.
You could just get Krylon in the color of choice and have at it but the result will be less than pleasing. When doing interior spray painting you are going to have over spray and runs.
To do it right,the case would have to be taken compleatly apart,preped,primered,sprayed,then reassembled without damaging your hard work.
The best arisol primer and finish paint will be bought at an automotive refinishing supplier at about $6-$8 a can. Now if you have an air compressor/spray gun it can be done cheaper.
Google DIY automotive refinishing and you'll see what i mean.
Galvanized