The Netherlands international spent 18 months at Old Trafford between the summer of 2015 and January 2017.
He struggled to make his mark in the Premier League and was allowed to head for France by Jose Mourinho.
Depay has, however, made no secret of where his allegiances lie as he prepares to head back to England on Wednesday.
The 24-year-old forward, who has rebuilt his career at Lyon, told reporters: "It is something special coming back to Manchester.
"The city is still red!"
United have seen City secure local bragging rights in recent years, with the Premier League title secured in record-breaking fashion last season.
Depay, though, still feels that the Red Devils are heading in the right direction under Mourinho.
He was given few opportunities to prove that he could form part of that project, having been signed by countryman Louis van Gaal, but accepts that he faced fierce competition for plans.
He said: "It would be easy for me to say Van Gaal gave me no freedom. Once you lose connection with the coach it gets difficult. United have a lot of attacking players. That is what they stand for."
He added on a frustrating stint at Old Trafford and the progress he has made since taking on a new challenge: "Everybody can see that. I can feel it myself. I have become more mature.
"When I came back, I felt like a different person. Everyone knows the history between me and Man United wasn't successful. I didn’t want it like that."
Depay managed just seven goals in 53 appearances for United.
He already has 28 in 70 outings for Lyon, with 22 of those recorded during a productive 2017-18 campaign.
His account has been opened in the current campaign and he will be hoping for more when returning to a Champions League stage against City.