Toronto. The earliest photos were monochrome – unless hand coloured. By the turn of the 20th century, colour photos could be taken using three black and white films sandwiched together and interspersed with colour layers. The additive colour system created transparencies while the subtractive system created colour negatives to print on colour paper.
One of the earliest commercial successes was the c1900 Autochrome glass slides sold by the Lumière Brothers of France. While only a single glass pate was used, dyed potato grains created the colours. Colour processes faced a quartet of issues: speed, resolution, fidelity, and permanence. The light from the scene had to go through many layers resulting in very low ASA ratings. In the late 1950s, Kodachrome slide film reached ASA 10 and had to be used only in sunshine! Other slide films reached an ASA of 32, but that too was better used outdoors.
The processes like autochromes were clearly low resolution since every filter was a tiny potato grain. While the mid 20th century colour films relied on dyes and colour couplers, the absence or intensity of the dyes were determined by their respective films, so grain did enter the question. Kodachrome and the other slide films were slow speed but high resolution. Colour negatives and prints on the other hand were faster but remained rather low resolution options until the 1970s or so. Detail and colour appeared to be trade-offs.
Similarly, in that era, colour fidelity was an issue. Film types were chosen for their beautiful and realistic renderings. No one film accurately captured every colour in a scene. Kodachrome was touted for the brilliant reds while Ektachrome and the like tended to give better blues and greens. White balance was an issue solved by blue and amber coated flash bulbs, special conversion filters, or colour films intended for use outdoors (blue sunlight) or indoors under incandescent lighting (soft yellowish colour). Enlargers had a wide range of different density filters (Cyan, Magenta, Yellow, Red) to balance lighting over all in a print.
The issue of permanence in colour films or paper was never solved before film lost out to digital technology. Some processes used small dye molecules limiting the choice so chemists balanced off fidelity and permanence. Today we live in a digital world where very high ASA (now ISO) ratings are common place and white balance is usually performed automatically. Modern day digital cameras (either stand alone or in smart phones) make correct colour rendering a snap – but framing, sharpness, subject matter, etc. remain issues for amateurs.