Each image is a composite of 3 individual photos. Each subject is photographed 3 times: once through a red filter, once through a green filter, and once through a blue filter. When shooting through a red filter, the result is a black-and-white photo of red-light only; same applies to the green and blue filters. Using Photoshop, the 3 black-and-white color planes are layered to create a color image.
Using only Black and White 35mm film to produce color images.