For retirees, who count as the sponsor for a dependent family, a non-citizen would also apparently have a blue bar on their Next Gen ID card.
Blue Bar: Non-U.S. Citizen Sponsors and their Dependents
The complication for a dependent is that their own citizenship status doesn’t matter for their card; even a citizen dependent of a non-citizen sponsor would have a blue bar on their dependent ID card. (I think.) So not helpful in this context.