When creating DVDs (I have used a home DVD recorder, cleanerXL, Sorenson, and Apple compressor (DVD Studio Pro)). I always notice that the luma and chroma of the outputted image seem to change. The image seems to get de-saturated and get brighter (with a loss of detail in the midrange). This is compared with fully uncompressed 10-bit footage that was either shot on DigiBeta or 35mm film. Of course there has to be a lot of data loss as you are going from uncompressed to highly compress MPEG-2.
I assume that the colour loss is because MPEG-2 is 4:2:0 (or something like that), not sure about the luminance changes though.
Within Compressor (for example) you can apply the gamma filter to saturate the colour a bit more and bring it back closer to the chrominance in the original footage. Using the gamma correction filter is always a trade off because while increased saturation is what you want you'll also be making your footage darker with increased contrast (lowering the luminance) at the same time. Make sure your footage can take the lowered luminance hit i.e. crushing the blacks too much or losing shadow detail. Start with a gamma correction setting of 1.1 or go 1.2 if you want a little extra. Encode 5 min. of test footage, burn your DVD and have a look at the result on a television to see if the result is what you're looking for.
Such is the nature of MPEG2 encoding. It always washes out the chrominance a little. And never by the same amount each time. It's all dependant on your subject matter.