Hi,
Not sure if this will help, but it might give you a step in the right direction.
Our GBM is a 2005 model year, but used the 2004 color codes. I don't know how long those codes were used. I do know the numbers are Sherwin Williams codes.
Our full body paint motorhome has the following colors:
Beige metallic Code # MB-47134(y)
Medium Bronze Pearl Code # MB-57763 0 (s)
Sage Metallic Code # MB-53911 0.
I believe the medium bronze is the darker brown in our color scheme, but it doesn't have a purple tint, so it's probably not the same.
If you do find the codes, I can highly recommend
PaintWorldInc.com as a highly reputable company with great customer service. They have various packages and products geared to the Do-It-Yourself-er, if you're planning on doing some touch up by yourself. They have products which help give a nice, smooth finish, 2-part spray epoxy clear-coat and a spray on "blender" which helps the new clear coat blend in with the old.
However, with the metallic paints, plus a vehicle that has over a decade of exposure, the match will be "close" at best.
Good Luck,
~Rick