Eye scientists have done extensive research about the retina which consists of 106 Million cells and all of them are light sensitive - rods and cones
Cone cells can distinguish colours and fine detail. There are approximately 6 million cone cells of 3 different types, each one being sensitive for a particular wavelength. There are extremely rare cases, where some people have 4 types or cone cells enabling them to see a lot larger light spectrum.
90 million rod cells are used for monochrome vision in dim lighting conditions. While they are highly senstive to light, they don't assist in colour vision as they only have 1 light sensitive cell.
Both of these cell types send the signals, they generate from light reflexes to the brain which then assembles the picture.