Im not sure if this applies to you but someone had a color difference too and it turned out to just be the player they were viewing it on.
They switched to a different player and the color was the same.
Something about the gain on one player I think. NOT SURE.
Along with the viewer difference, that GLenn alludes to, remember that MPEG-2 is a highly-compressed CODEC, and some data will be lost in the Export process. Some of that lost data will be in the chroma area, and also in the luminance area. These changes might well be noticed in a side-by-side monitoring.
As a test, Export to MOV w/ the Animation CODEC, and check that output against the original.