I've never seen a color code for the gauge faces.
Your best bet would be to have someone color match it for you. Automotive paint stores usually have chip books you could look thru to find a match, or they could use their computer gizmo to match it, although that might be expensive. One shop here charges $75 for computer color match.
If you can match it with a chip book, they can make you a rattle can with that color. I had a rattle can with custom color for $35.
