The color red causes our hearts to race, especially when we see it flashing in our rearview mirror. The most emotionally tense color, red is often associated with passion, beauty, blood, anger, danger, and, in other cultures, happiness. In a photograph red can either be the focal point or a great accent. Either way, there is something about red that draws us into a longer look at an image.
As a primary color in traditional color theory and as an additive primary in modern RGB imaging technology, red often is often buried in combinations with other colors in a quiet supportive role. But red can also be the star.
These three pics were all taken on the same day. In the image of the front of a truck, shiny red is the star of the photo. In the old Mobil sign red is contrasted well with the black. I like the red fire hydrant in the stonewall photo because it brings a pop of color to the early morning, muted tones of the wall. I think it also adds interest with the juxtaposition of nature and a man-made element.