Windows Media Player is hardly the most reliable QC tool. Get the export onto a properly calibrated TV. How does it look there?
It's not so much a colour reproduction issue as it is an artifacting/banding issue.
I cut it using a 5k timeline, and tried exporting it directly to a 1080p H264 file from there. I've also tried using AME to render down the 5k DNxHD master to a 1080p DNxHD file with unsatisfactory results - the file size is gargantuan.
Right now I'm attempting to export from a 1080p timeline with scaled down footage. Still waiting for my sample to export.
Clearly people have been editing and exporting clean RED footage to 1080 for some time now, yet it seems to elude me. What's your workflow?
I have not yet been fortunate enough to work with RED footage.
But for superior H.264 encoding, I do export out a lossless Intermediate using the UT codec, and from there I use an x264 encoder in Constant Quality mode. This produces better results than the MainConcept encoder Adobe uses with only CBR and VRB modes.