One of the challenges of street photography is to reduce the visual clutter and confusion you see all around you. You've got all types of people wearing all types of clothing, often crowded next to each other, surrounded by buildings, signs, billboards, utility poles, and more. Objects are in constant motion. Add color to the mix and the result is, more often than not, a visual mess. This is one of the main reasons why so many street photographers prefer to display their work in black and white: It takes color out of the equation, reduces visual distractions, and helps simplify the image.
That's fine if you're a fan of black and white and know how to avoid tonal mergers (a subject for a later discussion). If you prefer to shoot in color, there's another option, exemplified in the photo above. Instead of trying to simplify an image that has too many different elements competing for attention, try looking for compositions where the elements are already simplified. In the photo above, there are only three predominant colors: orange, blue, and black, with a touch of gray and brown. The shapes are large and bold. The patterns are simple and repetitive. These elements don't necessarily make this photo a masterpiece, but they do simplify the composition.
Here's another, slightly more complex example. The photo above has five colors: white, black, red, blue, and "flesh tone." (Yeah, I know. It doesn't match my flesh tone either. But can you think of a better name for it?) Although there's still a lot going on here, particularly with the spotted blouse and the map in the background with the dotted legend, it's a lot less than if dozens of competing colors had been in the frame.
These are by no means the only ways to simplify a composition. Other tools at your disposal include aperture setting for controlled depth-of-field, subject placement relative to the background, and focal length (wider vs. narrower). You're not obligated to use any of them--but if you do, your viewers will likely thank you for it.