Thanks LS_KING I was in the same position when I bought my McLaren grill. Its a tough choice, i like them both ways.
A regular LS lower bumper is all one color so it may be overkill with the all silver McLaren on a regular LS. Where the newer LSE's have the lower black bumper so a all silver grill isnt bad. I think you have to make it contrast what you currently have. If you have the lower silver grill I would do an upper silver/black grill. And vice versa.
KD00LS has all silver on a regular LS, it still looks good, but its a lot of silver
http://www.lincolnvscadillac.com/vbpicgallery.php?do=big&p=3260
This has the opposite color of the lower grill
http://www.kuruption.net/?cmd=showimg&iid=mclaren-ls03.jpg
where the newer LSE has the different color lower grill so the all silver grill isnt too much.
http://www.lincolnvscadillac.com/vbpicgallery.php?do=big&p=5634
Long post short, paint the middle of the grill the opposite color of your lower grill for a contrasted look.