Have'nt seen anything about the bottom colors on RX's. Mine is Silver with a darker color on the lower beltline. Can't find a code for that color.

 

What year? 99-00 has different trim code for silver than 01-03

 

I think the code is 051. Your Lexus dealer has it (unless you are thinking of another brand.)

 

You could also trying a local body shop, they can look up that stuff in a second. Tell them the year make and model and say "silver trim" and they can give it to you.

They'd honestly be quicker than calling Lexus since they'd have to ask you a million questions... name, vin, etc before they can tell you.