The Independent ran the article below which included a poll. Results were pretty close, with "green" slightly edging out black. Not sure how accurate, since the response was kind of low. I have a view of the bridge from my patio, and personally prefer black or dark gray to keep it historically correct for its setting, rather than a garish green.

https://www.newhavenindependent.org/index.php/archives/entry/grand_ave_bridge_update/