Colour choice is integral to graphic design. We can learn all the theories, follow the seasonal trends and understand the technical aspects when translating for web or print. But a large part of correct usage of colour is based on our instincts as designers.
One great way to build your confidence when using colour is to take time out away from your computer and play with the media you used to as a child – use poster paints, water colour, oils, chalk etc. Experiment with different textured paper, and draw. Draw from your imagination or from real life. Nature is a great point of reference, perfection in design. Take notice of how the colours change under different lights. Another good way is to study how other artists utilise colour.
Whenever I design anything, I always do it in black and white first. I may introduce greys in. But then I choose a colour palette which would communicate the message in the most effective way. Each step in the design process is exciting, but choosing the colours is a favourite.