Change gray color to a metallic gray

[cubelindo]

Hi there! 
This is my first post. I just begun recently to use Gimp and I'm trying to scan some of my Atari games boxes to make portraits for my game room.

The game I'm currently working on is one of the so-called "silver box" games, the gray color of the box has a metallic hue. I paste two photos (not mine, they are taken from AtariAge)





So, when I scanned my game, the gray was completely horrible and I erased it. I captured the color with a color capture tool from the photo I just posted and the result is:



So I tried to convert the gray to "metallic gray" I captures a pattern from the first photo and used the bucket to fill the second: horrible and tiled. Then I experimented with "light and illumination" but have not achieved any significant result.

I've watched some tutorials, but they mostlyt aim to make metallick effects with degradation, I don't think that will suit this design.

If anybody could hint me how to proceed, I would be very grateful.

Thanks!