Another good place to look for the original color is behind the voltage regulator on the firewall.
I don't believe that Brewster Green or Aspen Green were truck colors. At least not in the period 51-54. As far as I know (which may not be much

) the only dark green colors available for trucks from 1951-54 were either Forester Green or Juniper Green, depending on the year. These two colors were very similar. Here's a color chart online that shows the
1951-1954 Commercial Colors .