Color name: Springmist Green Metallic (color code P)
Paint codes...
Lucite: 4897L
Dulux: 4897D

You can see the color on this site here http://ultimategto.com/68colors.htm and here http://www.oldride.com/library/1968_pontiac_gto.html.

I also found a site that listed the Rinshed-Mason and Ditzler codes, http://www.myss396.com/ChevelleInfo/PaintCodes/1968_PaintCodes.html, where the code formulas for the color was verified from paint chip scans. Seafrost Green is Chevy's version of Pontiac's Springmist Green color.

Rinshed-Mason: A-1989
Ditzler: 43774