Question: Where does purple rice derive its color?
About the article "Rice", section "Nutrients and the nutritional importance of rice".

Candidate passages:
Glutinous rice is distinguished from other types of rice by having no (or negligible amounts of) amylose, and high amounts of amylopectin (the two components of starch).
Amylopectin is responsible for the sticky quality of glutinous rice.
The difference has been traced to a single mutation that was selected for by farmers.
Like all types of rice, glutinous rice does not contain dietary gluten (i.e.
does not contain glutenin and gliadin), and should be safe for gluten-free diets.
Glutinous rice can be used either milled or unmilled (that is, with the bran removed or not removed).
Milled glutinous rice is white in color and fully opaque (unlike non-glutinous rice varieties, which are somewhat translucent when raw), whereas the bran can give unmilled glutinous rice a purple or black color.
Black and purple glutinous rice are distinct strains from white glutinous rice.
In developing Asia, there is little regulation, and some governments have issued advisories about toxic dyes being added to colour adulterated rice.
Both black and white glutinous rice can be cooked as discrete grains, or ground into flour and cooked as a paste or gel. 
Black rice (also known as purple rice or forbidden rice) is a range of rice types, some of which are glutinous rice.
Varieties include but are not limited to Indonesian black rice and Thai jasmine black rice.
Black rice is high in nutritional value and contains 18 amino acids, iron, zinc, copper, carotene, and several important vitamins .
The grain has a similar amount of fiber to brown rice and like brown rice, has a mild, nutty taste.
In China, black rice is claimed to be good for the kidney, stomach and liver; these claims have not been independently verified.
Black rice is a deep black color and usually turns deep purple when cooked.
Its dark purple color is primarily due to its anthocyanin content, which is higher by weight than that of other colored grains but more limited in the number of different anthocyanin species present.
It is suitable for making porridge and it can also be used for making dessert, traditional Chinese black rice cake or bread.
Black rice was proclaimed as a 'superfood' worldwide largely thanks to an important piece of research by Dr. Zhimin Xu, titled "Black rice rivals pricey blueberries as source of healthful antioxidants".
The research stated that “just a spoonful of black rice bran contains more health promoting anthocyanin antioxidants than are found in a spoonful of blueberries, but with less sugar and more fiber and vitamin E antioxidants".
Several value-added products have since been launched using Black Rice.
These include noodles and Black Rice Cracker Chips.
In China, noodles made from black rice have been produced.
Thai black jasmine rice, while not as prevalent as the white and brown varieties, adds more vibrant color to meals, as well as providing additional health benefits. 
Nutrition and health.
Nutrients and the nutritional importance of rice.
Rice is the staple food of over half the world's population.
It is the predominant dietary energy source for 17 countries in Asia and the Pacific, 9 countries in North and South America and 8 countries in Africa.
Rice provides 20% of the world’s dietary energy supply, while wheat supplies 19% and maize (corn) 5%.
A detailed analysis of nutrient content of rice suggests that the nutrition value of rice varies based on a number of factors.
It depends on the strain of rice, that is between white, brown, black, red and purple varieties of rice – each prevalent in different parts of the world.
It also depends on nutrient quality of the soil rice is grown in, whether and how the rice is polished or processed, the manner it is enriched, and how it is prepared before consumption.
An illustrative comparison between white and brown rice of protein quality, mineral and vitamin quality, carbohydrate and fat quality suggests that neither is a complete nutrition source.
Between the two, there is a significant difference in fiber content and minor differences in other nutrients.
Brilliantly colored rice strains, such as purple rice, derive their color from anthocyanins and tocols.
Scientific studies suggest that these color pigments have antioxidant properties that may be useful to human health.
In purple rice bran, hydrophilic antioxidants are in greater quantity and have higher free radical scavenging activity than lipophilic antioxidants.
Anthocyanins and γ-tocols in purple rice are largely located in the inner portion of purple rice bran.
Comparative nutrition studies on red, black and white varieties of rice suggest that pigments in red and black rice varieties may offer nutritional benefits.
Red or black rice consumption was found to reduce or retard the progression of atherosclerotic plaque development, induced by dietary cholesterol, in mammals.
White rice consumption offered no similar benefits, and the study claims this to be due to absent antioxidants in red and black varieties of rice.
In science and nature.
The optics of purple.
Purple, unlike violet, is not one of the colors of the visible spectrum.
It was not one of the colors of the rainbow identified by Isaac Newton, and it does not have its own wavelength of light.
For this reason it is called a "non-spectral color".
It exists in culture and art, but not, in the same way that violet does, in optics.
It is simply a combination, in various proportions, of two primary colors, red and blue.
In color theory, a "purple" is defined as any non-spectral color between violet and red (excluding violet and red themselves).
The spectral colors violet and indigo are not purples according to color theory but they are purples according to common English usage since they are between red and blue.
In the traditional color wheel long used by painters, purple is usually placed between crimson and violet.
In a slightly different variation, on the color wheel, it is placed between magenta and violet.
This shade is sometimes called electric purple (See Shades of purple).
In the RGB color model, named for the colors red, green and blue, used to create all the colors on a computer screen or television, the range of purples is created by mixing red and blue light of different intensities on a black screen.
The standard HTML color purple is created by red and blue light of equal intensity, at a brightness that is halfway between full power and darkness.
In color printing, purple is sometimes represented by the color magenta, or sometimes by mixing magenta with red or blue.
It can also be created by mixing just red and blue alone, but in that case the purple is less bright, with lower saturation or intensity.
A less bright purple can also be created with light or paint by adding a certain quantity of the third primary color (green for light or yellow for pigment).
On a chromaticity diagram, the straight line connecting the extreme spectral colors (red and violet) is known as the line of purples (or 'purple boundary'); it represents one limit of human color perception.
The color magenta used in the CMYK printing process is near the center of the line of purples, but most people associate the term "purple" with a somewhat bluer tone, such as is displayed by the color "electric purple" (a color also directly on the line of purples), shown below.
Some common confusion exists concerning the color names "purple" and "violet".
Purple is a mixture of red and blue light, whereas violet is a spectral color.
On the CIE xy chromaticity diagram, violet is on the curved edge in the lower left, while purples are on the straight line connecting the extreme colors red and violet; this line is known as the line of purples, or the purple line. 
Computer web color purples.
Purple (HTML/CSS color) (patriarch).
This purple used in HTML and CSS actually is deeper and has a more reddish hue (#800080) than the X11 color purple shown below as "purple" (X11 color) (#A020F0), which is bluer and brighter.
This color may be called HTML/CSS purple.
It seems likely that this color was chosen as the web color purple because its hue is exactly halfway between red and blue and its value is exactly halfway between white and black.
A traditional name sometimes used for this tone of purple is patriarch.
The first recorded use of "patriarch" as a color name in English was in 1925.