Red lentils are actually more orange in color.
With their skins on, they actually wouldn’t look either orange or red. They are sold to us “hulled”, meaning with the skins removed. Some Red Lentils are the same lentils as brown ones are, but with the skins removed. Canada, the largest exporter of lentils in the world (as of 2004), mostly grows the kind of Red Lentils that originally had a brownish-green skin.
The names of these varieties include Crimson, Redwing, Redcap, Robin, and Blaze. In India, this kind is more generally just referred to as “masoor dahl.” In America, a popular variety is Red Chief, which grows with tan skin on the lentils.
Some feel that hulled Red Lentils have less taste than other lentils, as a lot of the flavor was in the skin.
Red Lentils will cook to form a purée, while Green (aka Brown) Lentils stay more whole and separate because they have their skins on — thus these are better for salads and stews, while red is good for soups, etc.
All Red Lentils turn a golden color when cooked.
See also main entry on Lentils.
Don’t presoak. Will cook in about 10 minutes, and after that turn to mush, so test them as they approach the ten-minute mark, and if you need them to stay intact for what you are making, be ready to whistle them out of the water. To get them puréed, let them simmer for about 20 minutes.
To pressure cook: don’t presoak. Put in pot with 3 times as much water as lentils. (e.g. for 250 g / 1 cup of lentils, add 750 ml / 3 cups of water.) Cook on high for 4 to 6 minutes, depending on whether you want the lentils intact or mushy.