I read an article and someone mentioned traveling alot and paying attention to your exit routes.
I beleive it's be more of a building code issue, or even an Engineers preference... Frankly I think its the diode designers thinking there seeing red and will have none of it!
In researching for this post, I haven't been able to find in the Ohio Administrative Codes any information regarding the use and/or requirements regarding green exit lights. Most of the requirements are in reference to energy codes. I believe THIS would have the authority to do so.
Not sure what part of Ohio you are from. Your local building department may have the answer.
Heres a link to a company under the umbrella of Hubbell, Dual Lite,
Adobe or flash might be required, not sure, a slide show shows a red exit signs on there main page. They do make both. http://www.dual-lite.com/products/index.php?c=405318&p=d2
Specifications for accident prevention signs and tags. Also covers what colros and lettering must be for other types of signage or instructions. This may help