Like finding any lipstick colour, finding the right red is a matter of trial and error. Do you have a favourite make-up brand? If so, go to their counter and just try out every colour on your hand, or ask an SA to try it out on your lips, or for a recommendation. MAC has tons of colours, so that might be a good place to start.
Red is never just red, there are so many different variations on it and it can give a totally different look. Some have more blue undertones, some more orange...if you have a tan, you can go for a warmer red.
I was lucky in finding my perfect red lipstick. I wanted just a splash of colour, something dramatic for going out whilst keeping the rest of my makeup very neutral. I went to Armani and had an amazing SA who picked out my perfect colour in one go. I was very skeptical because I'm really pale, I thought it might look too shocking. Also, beware, the colour of the stick is not the colour that goes on your lips, so don't pass something up until you've tried it. My lipstick is very dark but when it goes on, it's the perfect ruby red...and it is
Giorgio Armani Lipstick Mania number 9
Good luck in finding your perfect colour, it's really worth it when you do