I had a bright red interior in my GS and found it somewhat of a novelty at first but that it became unnoticeable over time, not harsh. When I actually stepped back and noticed it I liked the fact that it was different to all the normal black interiors.
If I had a choice at the time I wouldn't have chosen red, as I didn't purchase new and there were no others available there wasn't a choice, but I didn't regret it once purchased.
The RX is a little different, but the red is much darker which probably suits the vehicle better (unless you are looking at the F Sport).