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The colors do not stand out enough and need more contrast between them to make this pop! Try using more of a chocolate as your dark brown and try some other colors other than brown such as tan, faded blue, just play around with using different colors. You can find sites that will help you match colors together better such as http://kuler.adobe.com/.

Yeah when making it i wasn't sure on how to work with the colours, you are right, needs one more colour used.