Color theory primary colors work at all is that the imperfect pigments being used have sloped absorption curves, and thus change color with concentration. A pigment that is pure red at high concentrations can behave more like magenta at low concentrations. This allows it to make purples that would otherwise be impossible. Likewise, a blue that is ultramarine at high concentrations appears cyan at low concentrations, allowing it to be used to mix green. Chromium red pigments can appear orange, and then yellow, as the concentration is reduced. It is even possible to mix very low concentrations of the blue mentioned and
Orange (colour) from the photosynthetic pigments called carotenes. Orange is a very common colour of fruits, vegetables, spices, and other foods in many different cultures. As a result, orange is the colour most often associated in western culture with taste and aroma. Orange foods include peaches, apricots, mangoes, carrots, shrimp, salmon roe, and many other foods. Orange colour is provided by spices such as paprika, saffron and curry powder. In the United States, with Halloween on 31 October, and in North America with Thanksgiving in October (Canada) and November (US) orange is associated with the harvest colour, and also is the colour