The paint code for all GMC trucks and SUV's are located on the service parts identification sticker. While the sticker is moved around from year to year, it still in your glove box on the Sonoma. Most labels are white paper sticker, while more moderns ones are a silver label. Most paint codes in our database start out with a "WA", most cars and trucks will start out with a "BC/CC U". BC/CC stands for basecoat/clearcoat, and the U stands for upper or body color.
Two Tone Models: A two toned car will have a "U" followed by the four digit color code for the body color, and an "L" followed by a four digit color code for the lower color or the bumper color.
Color Code 11 Pewter Met
Color Code WA382E Pewter Met
Option that is close to what you described would be the gold color
Color Code 60 Gold Met
Color Code WA398E Gold Met
Good luck and hope this helps.