Colour is complex and there are no perfect guidelines for choosing the right colours for your package design, but here is a start.
1. Keep it simple and try to use two or three colours that complement each other. People like simplicity and this will make your package easier to understand.
2. Try to use contrast to make the different aspects of your package stand out.
3. Think about your target market. Blue is liked universally by both genders, while this is not so much the case with for example purple. Men tend to prefer bolder colours.
Be aware that cultural perception plays a strong role in which colours are appropriate, which in turn can influence colour choices. Test, test, test and evaluate the results.