Newco chief-executive Green has called for Gers supporters to get behind him and his partners by buying season tickets.
However, the Glasgow club's followers had vowed not to put their hands in their pockets until the businessman sold to the Walter-Smith-led takeover group.
Now that Smith and Co. have pulled out, it remains to be seen whether the fans will plough their cash into the club.
Andy Kerr, president of the Rangers Supporters' Assembly, told Green fans need to know what their plans are – as it was revealed city property developers Allan Stewart and Stephen McKenna want to buy Rangers for a reported £11million.
Kerr said: "The fans' contribution via season tickets is around £20million, and I am sure most are keen to plough that money in and get the club's coffers up.
"But we don't just want to hear words about how much Mr Green and his associates plan to invest, we need written assurances.
"Mr Green and his consortium own the club and we want to support them. But we want to be sure we are pushing in the right direction.
"The reality is that for the next five years everything is going to have to be cut back, with no return on investment."
Despite claims they want to make Rangers successful again, Green and his consortium have been dogged by accusations they are out to cash in on the club.
Kerr reckons fans will need to know their money will go into restoring the fortunes of Rangers instead of lining the pockets of investors.
He said: "What is concerning us is our season-ticket money and the sale of our best players being used to fill the club kitty.
"It was interesting to hear that Walter Smith and his party withdrew when they didn't get assurances on some of the things they needed to hear. We need evidence about what Mr Green plans to do."