According to experts, colour undeniably affects your mood.
Red for fear, anger and passion - use it sparingly, such as in a clutch or nail polish.
Blue for relaxing - great for first dates and job interviews.
Green for refreshed or relaxed - looks good on every skin tone.
Yellow for joyous and happy - don't wear too much unless you want to look like a walking banana.
Orange for enthusiasm and creativity.
Purple for confidence - good for job interviews.
Black for formality - it can either be a downer (think villains or funerals) or tres chic (think Audrey Hepburn).
See this Huffington Post article for more information.
Regardless of what effect colour has on our moods I think we all need to inject a bit more of it into our wardrobes, especially as the weather turns grey.