Is there a way to stop colors flattening when encoding for the web and DVD

Hi. I am in post prod on my first feature film, which has some great horror dream sequences, lit red and green in the Mario Bava tradition. They really do look stunning in the original footage, with highly saturated crisp colors (We had a really great cinematographer) But when I try to create clips for the web, the colors flatten a lot. They look better on my i-phone than my Lcd computer monitor. doing DVD outputs also looses something, but less so. It depends on the playback equip. My plasma TV and upscaling dvd player make them look fairly good. The footage is progressive scan 25 frames per sec HD. (16:9 cropped to 2:35:1) Does anyone know the optimum settings for web encoding have just used 310x710 pixels using H264 compressor at 3000 kbts per sec