Well................it depends on two things..............do you want realism and how much work are you willing to do.
If you want realism, read on. This is one way it can be done.
As you can see the faces or busts are created using covers on the stadium chairs.
Some of the chairs have multiple colors in each cover as seen here.
You can easily isolate a singe white chair. Just remember you may have to isolate several chairs from the different sections because they will all have slightly different perspectives.
Make copies of the isolated chairs chairs and align.
Then colorize the chairs either in groups (with masks) or individual chairs with a Hue & Sat layer.
Giving the chairs multiple colors would be just a matter of masking two chair layers. (Bottom chair)
Making the graphic is simple, just use an image and convert with posterize, cutout filter, or Patchwork filter. Then free transform for the right perspective, overlay, reduce the layers opacity, and color the chairs accordingly by sampling the colors from the overlay.