Nepenthes singalana pitchers are sometimes green or red, but are often very, very dark. Nepenthes ramispina has some of the darkest pitchers in the genus. These vigorous little hybrids are almost guaranteed to be very dark.
These are from a single clone in tissue culture, BE-3829.
Sun: Grow on sunny windowsills with at least three hours of direct sun, in greenhouses, or in a terrarium with fluorescent light
Water: Water with distilled or purified water frequently, do not let the pots sit in water for long periods of time but be sure to keep the potting medium moist all the time
Temperature: Daytime temperatures in the 70’s-80’s with a 10-20 degree drop in night temps
Dormancy: none needed