The bright colours of flowers help to make them more visible to insects and animals to assist in the spread of pollen and seeds. The perception of colour by humans is a complicated process of interaction involving the physical qualities of the object, the intensity of the light, the perceiving subject, and the cultural context of the perceiving subject. The wavelength of light determines colour. If sunlight is passed through a prism, as Sir Isaac Newton first did in the late 1600s and early 1700s, all the rainbow colours of the spectrum are revealed. What appears to be 'white light' is actually a combination of light of red, orange, yellow, green, blue, indigo, and violet.
Objects appear to be different colours because they absorb some wavelengths and reflect others.
A green flower absorbs all coloured light wavelengths except for green which it reflects. Photoreception is the general scientific term used to describe the biological responses of organisms to light. Photosynthesis is the specific method by which green plants utilise light energy to transform water and carbon dioxide into their necessary carbohydrate sustenance. In animals rods and cones are the names given to the two different types of photoreceptor cells in the retina which affect visual perception. Rods primarily influence visual perception when the light intensity is low or dim.