Green is facing a Scottish Football Association charge after being served a notice of complaint and has being given until April 17 to respond.
Regan said: "It's very surprising and it's very frustrating when we are all trying to build a stronger and more positive game for the future.
"It's not helpful for anybody irrespective of who it is to be using the kind of remarks that were used at the weekend but we need to give Mr Green the chance to explain himself and that's what we have done.
"We saw Mr Green's comments at the weekend and our compliance officer has chosen to issue him a notice of complaint. We have written to him to ask him for his feedback and asking for the background to comments he made and until we have got that it would be wrong to speculate on what happens next."
Regan added: "The Scottish FA have a very clear policy about dealing with any racist or discriminatory behaviour and it's in our strategy Scotland United.
"It's our job to engage with black and ethnic communities to build stronger relationships for the game therefore anything that challenges that is something that we take very seriously."
The notice of complaint refers to the Disciplinary Rule 66 and Disciplinary Rule 71 which guard against comments which bring the came into disrepute and those which are not in the "best interests" of the SFA.
In an article on Sunday, Green, a Yorkshireman, said: "I was brought up in a mining community where whether someone was black, white, Catholic, Salvation Army, Protestant, made no difference.
"When I played at Worksop Town, the other striker was 'Darkie' Johnson. Now if I say that today I could go to jail.
"You know, Imran (Ahmad, Rangers director) will come into the office regularly and I'll say 'How's my Paki friend?'"
Following the publication of those comments, Green released a statement insisting that he "deplores'' racism and sectarianism, while accusing Show Racism the Red Card - which reported him to the SFA - of a "knee-jerk reaction".
In a statement on Monday, Green said: "It is unfortunate that Show Racism the Red Card has fallen into the trap of taking something out of context and giving a knee-jerk reaction.
"In the interview, I referred to the fact we are now living in a politically correct world where words and phrases that were once used are no longer acceptable.
"My use of the word 'Paki' was when I was referring to how I sometimes warmly address my colleague and friend Imran Ahmad when we meet, something we both know is light-hearted.
"I deplore racism and sectarianism and this football club does a huge amount of work in this area to help eradicate these problems."