Red is an important color in photography.  Whenever you have something red in your photos, this subject will get attention. Our eyes see the color red first. I like to include red in my photos.  A good example is a hiker in the forest showing the huge trees.  To really show the size of the trees it is best to put a person in for scale.

© Wolfgang Kaehler

If the hiker would have a green or brown jacket he or she would get lost, but with a red jacket the hiker sticks out and everyone can see the hiker.  Fire engines are red because they are visible and have to move quickly through traffic.  Red flowers attract bees for pollination; red barns are picturesque standing in a green wheat field; male Cardinals are red to attract a mate.