Of course one can make color photographs with a pinhole camera. It depends only on the recording material. Because pinhole pictures have relative you may want to use film with high contrast or increase the contrast when developing the shot.
I like to add digital grain. Besides of liking the look of grain (and that of some digital noise) there are two reasons for it:
- By comparison the grain is sharp; it replaces the missing sharpness.
You can make quite sharp photographs with pinhole cameras, but not with a DSLR with FourThirds sensor as I use and self made adapter. The “ideal hole” is not within reach for my skills. My holes are always too big.
- Grain hides sensor dust.
Dirt on the sensor is inevitable visible with such tiny apertures (in my case ca. f/120). In spite of the very good self cleaning system of Olympus that makes dirt irrelevant on normal pictures I have to clean digital pinhole shots much. Some dust is visible nevertheless. I cannot stamp that elaborately and accurately. Digital grain makes it nearly invisible.