Q: Why isn't my Venus flytrap red like in the photos?
Red traps
A: Photographs of Venus flytraps often show plants with
vividly colored, crimson or scarlet traps. Plants
cultivated by beginners usually do not have this amazing coloration. Why?
The traps of Venus flytraps only turn that intense color if they are
getting plenty of bright light. With less than bright light, they
revert to a light green color, perhaps with only a smattering of red on the
lobes.
Some varieties of Venus flytraps have been selected by horticulturists because they are
naturally deeply colored. In addition to having red traps, the entire plants are deep red.
Noteworthy examples are Dionaea 'Red Dragon',
D. 'Red Piranha', and
D. 'Colin's Red Sunset.'
There are other pretty flytrap cultivars, though, that do not have the deep red
coloration. For example, Dionaea 'Justina Davis' has no
red coloration at all, and has a a lime-green sort of appearance.
Page citations: Rice, B.A. 2006a; personal observation.