It's a "personal" preference. If YOU[/color] like it--do it--it doesn't matter what others like.
If you are not sure, maybe put some black electrical tape over the red (you can easily cut to fit with an Exacto knife or razor blade and see if you like it--if so, then go permement with black as you desire. Maybe the black tape will be good enough--you'll know when you do it. And if you don't like it as well as you thought, then tape is easy to peel off.
I personally like the red, its a nice contrast on the grill. That being said its strictly personal preference. For those of us who prefer red, you could probably find an equal number that would would prefer black or even another color.
This is really a pretty common modification among the custom truck scene. It looks good when the letters are color matched to the rest of the vehicle. I'm hoping that someone makes some nice billet letters.