Got some interesting info from this article:
http://www.wdc-jp.biz/pdf_store/jspcmb/ ... _3_235.pdf
Wonder if you guys have read it before.
"The article was studying the effects of the five macro - components and sucrose
in half strength MS (1/2 MS) agar medium on red-color pigmentation in the plant bodies of Dionaea muscipula and Drosera spathulata generated from multiple shoots in vitro.
In 1/2 MS agar medium modified with 10.31 mM NH4N03 and 9.40 mM KN03 and supplemented with 0.75 or O% sucrose, the subcultured plants continuously proliferated by multiple shoots and generated large, green-colored plants, while with dilution of those nitrogen components and increase of sucrose to 1.5%, the red-color anthocyanin pigmentation spread from the glands or glandular hairs to the entire leaves and the plant sizes and dry weight decreased in inverse proportion to the depth of red color.
...
Insects contain total nutrients of N (99- 121 g/kg dry weight), P (6- 14.7 g/kg), K (1.5-
31.8 g/kg), Ca (22.5 g/kg) and Mg (0.94 glkg) (Reichle et al., 1969; Dixon et al., 1980; Watson et
aL, 1982) that are somewhat smilar to the medium requirements studied here. Prey would be more attracted to and captured by red-colored plants of Drosera species than by green-colored ones. Generally, carnivorous plants might have adaptation strategies to barren, wet and low pH soil conditions by interaction between leaf carnivory and low root consumption of nutrients (Adamec, 1997). The present study suggests that the two species would
turn red color when they became deficient in nitrogen compounds to make themselves attractive to prey and would catch more prey if they had too low a root consumption of llutrients to survive, grow and propagate. The anthocyanin pigmentation in the two species may make it possible to be biosensitive to nitrogen consumption uptake."
Basically, in simple terms, when the plant is sufficiently supplied with nutrients(i.e. it has eaten more insects), it is stronger and grows more. However, it cuts back on red-pigment production.(or red pigments are masked by increased chlorophyll production. The article did not discuss this.)
When the plant is nutrient deficient, the plant becomes more strongly coloured to attract more insects(the ones with nutrients) for the plant to grow more healthily.(as in the study, those who were red were less robust than those who were sufficiently supplied with nutrients(the green ones))
That's probably why feeding your plant insects may cause it to have less pigmentation. I found that an interesting read and decided to share it.