Psychology of Color
One of the biggest mistakes people make is to choose their theme based on their personal preferences for layout and colors. You can have the perfect layout and great material on your site and yet, people will just not like the site. So you need to ask yourself, "why do people not like my site?" or "why aren't they buying from my site?" The answer is probably that your theme uses a color that is sending out a very different message to your viewers' brains. This is a subject of protracted discussion and there are college courses on this subject. Professionally it is referred to as psychology of color. Your best bet for online information on colors is at http://www.pantone.com.