REDRushes Color Shift

I just received RED footage shot at 4096x2048. I plan to edit that in the Avid. Without putting a resize on it (besides the RENDER Half Res Standard), it is not 16x9 format, thereby placing black bars on the top and bottom.

I wanted then to resize the image, cropping off the left and right, to fit it into the 16x9 workspace without squeezing the image. I used these settings:

RENDER; HALF RES Standard
TC: EXTERNAL
LOOK SOURCE: CAMERA
COLOR SPACE: REC709
GAMMA: REC 709

RESIZE:
CROP: DO NOTHING
SCALE CHECK CHECKBOX 1920x1080
FIT: Height
RESAMPLE: CATMULROM

OUTPUT
QTMOVIE
H.264
REEL ID FULL NAME

The oddity I found, however, is that there is a slight color shift towards the magenta side. It's not an issue, as these are just dailies to edit from. I would just like to know why there is such a difference in color. Because the color space and the gamma was REC 709 both times I exported as H264 Quicktimes both times, I can only point the finger at the resize causing the color shift. Perhaps the Resample selection?