If you mean you've never seen one, I can't argue with you. I don't recall ever seeing one either. I'm not sure that's enough to conclude they didn't make them during WWII though.
How many Toolmobiles have we seen? Less than a dozen? How many have we seen that had an indisputable original red finish? My point is they're rare enough to begin with and maybe the green ones are even rarer.
The catalogs also indicate otherwise. The Toolmobile was included in every wartime catalog (18A, 19, 19-A, and 19-R) from 1941 to 1946. It is always shown, like every other toolbox, as red, and called "brilliant Chinese red" in the text. But we know they painted their boxes green during the war, they just re-used the same graphics from before the war. Catalog 19-A, which dates from 4/1943 to NLT 1/1944, is the first catalog Plomb addresses WPB requirements and restrictions, reusing catalog 19, but including notes about finishes and availability in the Price List inserted in the back. Catalog 19-R, which dates from 2/1944 to 10/1946, is the first catalog Plomb makes the annotations in the catalog itself, striking through items that are discontinued with red lines and adding DISCONTINUED and other notices about availability. One of those notes is in the toolboxes section. References to "brilliant Chinese red" are struck through with red lines, and a note in red text reads, "All toolboxes finished GREEN." Some of the toolboxes (those the WPB deemed redundant) have been struck and discontinued. The Toolmobile is not one of them.
Let me emphasize, that is not an argument that they made them. Empirical evidence is better than documentation. But it is an argument that the catalogs certainly suggest they made them, and if they made them, there is no indication they wouldn't have been GREEN like "all" the other toolboxes.