Thanks for all the comments. To be clear, the idea isn't mine, but a team member's from an OpenIDEO meet-up; I was just the only one with a computer and a profile at the time. Yes, the social stigma was part of the idea; you wouldn't go on a date if your card was red. Thus, spending less.
In terms of apps, there are already lots of companies already developing phone and apple watch apps for financial management (I work for one of them). These devices are not always owned by the people who need financial empowerment the most, so not sure about implementing the idea as an app. I guess there could be a program provide free devices with a financial app already installed on it to lower income individuals. Like a watch with only one app on it; a fitbit for financial empowerment.u
One community hub can be the banks themselves. When someone without online banking access or a smartphone cashes a check, the teller can hand them a a card with a quick savings recommendation or tip. One of these cards can give the opportunity to get a free smart phone with a financial app already installed that only includes the most basic and pertinent features for financial literacy/improvement.