Trouble with color exchange

[astronaut]

I am very new to Gimp, and my goal with this image is to change the brick red to fuschia. So far, I have Indexed the Image Mode to 32 colors max, and I am having trouble with using Color Exchange. I chose the "From color" from the image itself, and I want the "To color" to be fuschia. I have tried messing with the red/green/blue thresholds, but I think I am missing something. 

Thanks in advance!