Same files played directly to external monitor from dv tape look good. Same files played from a WMP file look good. Same files on a VCD, look good. Go to DVD via DVDA, colours are washed a bit. Need to re-calibrate monitor for richer colours everytime.
So, are you saying that one shouldn't "assume" that that which works for "other" authoring - WMV, MPEG [non-DVD authoring] - is not always going to give the same result? I didn't know that. So I must consider lowering the gamma before rendering to MPEG2. Is this something you do to?
Are you using a set top player to play your DVDs? Please be aware that some set top players have settings that adjust colors. For instance, some Sony players support "picture modes" (e.g. standard, dynamic, cinema, etc) which adjusts the brightness, contrast, color, and hue.
I always run multiple tests of my videos on various DVD players in combinatioon with various TVs. That is how I came up with that answer. Videos lighten either during the Mpeg 2 render in Vegas or in the authoring using DVDA. Try lowering the gamma until it looks a bit on the dark side on your monitor after you color correct and see if it doesn't inprove the colors.
Kick the saturation level up a bit if it is starting to get too dark and it still doesn't have enough color, but I don't think that will be necessary.
I should also note that most of my videos are under stage lighting conditions so they always have to be color corrected. I set the black and white points carefully and then lower the gamma as a general rule if the end product is a DVD using DVDA. For VHS It's different because the media can't take the color saturation. I tend to use my Proc Amp for that.