I agree and I have heard there will be red accents in the uniform. I think they haven't done more red in the cabin because it isn't as soothing and calming as the blues/grays. I think they could have at least gone with red pillows and cloth head rests.
Depending on what study you read and/or believe, red is the color of aggression. Apparently reds can induce fits of rage. Maybe that's why NW has shied away from putting red in the cabin.
On the other hand, red is also associated with people eating more food at a restaurant. Maybe NW should put red in their cabin to drive sales of their (awful) snack boxes?
-RM