Well, several biological and scientific explanations for this that I know for a fact:
1) The natural colours of danger in nature are red, yellow and black. Most dangerous animals are dressed in lively colours such as red, yellow and black (think of bees and wasps, or exotic frogs.) Their most common colours are those and tell us they are dangerous and to steer away from them.
2) The human eye only picks up three colours, red, blue and green (thats why we have RGB monitors, there is no need for any other colour). Green and blue were very common colours in the past (well, the way the world is going I don't see much green anymore...) so as Jynx said, the human eye has developed to be sensitive to those colours. Dogs only see blue and green.
3) Actually, blue and green in light catches our attention much more. Simple red lasers are ofte used as pointers because red light 'disturbs' the eye less. A green laser can be quite painful to look at and blue LEDs are unbearable. The body is used to receiving blue light as a way of waking up (the sky is blue, it means the sun has come up and reduces the amount of melatonine in our body, which makes us less sleepy and wake up).
However, since we are more 'used' to blue and green, red draws its attention. If we did live in a world with lots of red, it wouldn't catch our attention as much (despite what is said above), and if we lived in backgrounds for thousands of years, the genes in the eye would mutate and turn red into the 'common colour' and maybe then blue or green would be the colour to draw attention to itself.