The color is in the pigments Xanthophylls such as zeaxanthin are found in highest quantity in the leaves of most green plants, where they act to modulate light energy and perhaps serve as a non-photochemical quenching agent to deal with triplet chlorophyll, which is overproduced and alcohols; Zeaxanthin is one of the most common carotenoid alcohols found in nature. Synthesized in plants and some micro-organisms, it is the pigment that gives paprika which is made from bell peppers.

The term carotenoid refers to a family of about 600 different plant pigments that function as antioxidants . The yellow, orange, and many of the red pigments in fruits, vegetables, and plant materials are usually carotenoids. In fall, when deciduous trees prepare for winter and stop their chlorophyll production, the green color of the leaves fade and the orange, yellow, and red colors of the carotenoids in the leaves are revealed before the leaves die and fall to the ground. Plants appear to produce carotenoids to protect their stems and leaves from the energy of the sun. Ultraviolet (UV) wavelengths can generate molecules called free radicals that can damage living cells. Free radicals are molecules, or fragments of molecules, that are unstable and highly reactive. Free radicals are produced as the result of a normal molecule losing or gaining an electron. In normal, stable molecules, electrons associate in pairs. However, radiation from the sun can result in the removal of an electron from a molecule and the formation of free radical. Carotenoids as antioxidants limit free radical damage by donating electrons to quench, or neutralize, the oxidant radicals.

Bell peppers are an outstanding source of antioxidant and anti-inflammatory phytonutrients. These phytonutrients include flavonoids (luteolin, quercetin, hesperidin) and hydroxycinnamic acids (especially ferulic and cinnamic acids). But the hallmark phytonutrient group found in bell peppers is the carotenoid family, with more than 30 different carotenoids being provided by this vegetable. Included in bell pepper carotenoids are alpha-carotene, beta-carotene, cryptoxanthin, lutein, and zeaxanthin. Bell peppers are an excellent source of antioxidants vitamin A and C as well as nerve-supportive vitamin B6. Bell peppers are a very good source of heart-healthy fiber, vitamin E, folate, potassium, and vitamin K as well as the enzyme-supportive molybdenum. They are a good source of bone-building manganese and magnesium, energy-producing vitamins B1, B2, B3 and B5.