Red cultivars will flower, but their seed yield usually isn't worth it. Our Akai Ryus produced a staggering 3 seeds this year....
Could it also be a function of age? My red flytraps flower every Spring and achieve a very dark color while grown outside; and often attempt a second round of blooming by Fall -- but they are also several years old . . .
“Sì perché l'autorità dell'opinione di mille nelle scienze non val per una scintilla di ragione di un solo . . ."
-- Galileo "Biff" Galilei
My D. 'Akai Ryu' gets nice and dark with only 4-6 hours of direct sun. Try a little dappled shade. Some plants give their best coloration with some shade, others don't.
Grand Hotel... always the same. People come, people go. Nothing ever happens.