The paint scheme is a simple three color one. Upper base of a tan, lower light blue and the green is freehanded with the airbrush. Models like this make great test mules to practice on. If you don't like the way it turns out, give it an overall coat of a light gray and start again and again. Practice by doing solid colors first, making sure you are getting a even coverage. You can practice this by doing a light base coat then apply a darker one. Watch the pattern your airbrush lays down. You can adjust the pattern by the distance you hold the airbrush from the model while spraying. **Remember light coats are better than solid thick ones.**
What type of airbrush are you planning on using, single or double action?
Trace an outline of your model on a large piece of paper. Use some cheap acrylic paints to practice your strokes. Once you're comfortable with doing base coats, then try free handing details such as blotches, lines, patterns. You'll do well, just takes a little time and practice. Building models is the same, clunky at first, refined later.
Cheers!