Players from the Turkish team were furious after assistant coach Pierre Webo was shown a red card by referee Ovidiu Hategan of Romania at Parc des Princes, saying Coltescu had used a racial term to describe Webo, who is from Cameroon, before he was sent off.
Basaksehir substitute Demba Ba demanded that the fourth official explain himself, while PSG players Neymar and Kylian Mbappe also demanded an explanation. Basaksehir coach Okan Buruk said "you are racist" to Coltescu.
The score was 0-0 when the incident took place about 14 minutes into the match.
UEFA said the match would resume on Wednesday evening with new officials.
"Following an incident at tonight's UEFA Champions League match between Paris Saint-Germain FC and Istanbul Basaksehir FK, UEFA has — after discussion with both clubs — decided on an exceptional basis to have the remaining minutes of the match played tomorrow with a new team of match officials," UEFA said late Tuesday.
"A thorough investigation on the incident that took place will be opened immediately," it added.
Television footage captured the exchange between the fourth official and the referee, with Coltescu telling Hategan that Webo should be reprimanded for his behavior on the sidelines:
"Go and give it (the red card) to the Black one, this is not possible (tolerable), go and identify him, go verify, the Black one over there," Coltescu allegedly said, in Romanian, about Webo.
Webo was enraged and was heard to repeat at least six times "Why you say negro?" as he sought an explanation from Coltescu.
Webo, who was visibly distressed, then added: "He can't say negro, he can't say negro."
At this point, Ba could be heard also questioning what Coltescu had said.
"Why is the fourth official saying 'negro?'" Ba said twice.
Moments later, Ba then came off the bench and stood in front of Coltescu and said: "Why when you mention a Black guy, you have to say 'This Black guy?'"
During the interruption, Basaksehir posted a message on Twitter against a UEFA backdrop with the message "NO TO RACISM."
PSG defender Presnel Kimpembe, who was on the field during the game, also posted that message on his Twitter account.
Mbappe expressed his support for Webo on Twitter.
"SAY NO TO RACISM," he wrote. "WEBO WE ARE WITH YOU."
Former Manchester United defender Rio Ferdinand, who played 81 times for England, said it was crucial that UEFA now responds strongly.
"We're at a disturbing tipping point, not a week goes by without an incident involving race," he told broadcaster BT Sport. "The players walking off is a step in the right direction, but it can't just be left to them."
Piara Powar, executive director of the anti-discrimination Fare network — which helps UEFA investigate cases — told The Associated Press there was no excuse for Coltescu's language.
"Unintentional racism is still racism," Powar said in a text message to The AP. "If officials cannot set the standards by their own behavior, they cannot be relied on to deal with racism on the pitch or in the stands."
Like Ferdinand, he also thinks more has to be done by those running the game.
"The walk off by both Basaksehir and PSG together lays down a marker in Europe," Powar said. "Many players are fed up with half measures to tackle racism, and are more prepared than ever before to exercise their right to stop a match."
The 38-year-old Webo is a former Cameroon striker who made more than 50 appearances for his country's national team. He played for Basaksehir from 2011-13.
Seven years ago, Hategan was in charge of a match between CSKA Moscow and Manchester City when City's Black players were racially abused.
City captain Yaya Toure directed referee Hategan toward fans making monkey noises at the English club's Black players.
Michel Platini, UEFA's president at the time, requested an internal inquiry involving the referee to examine why guidelines were not followed to respond to discrimination incidents during matches.
UEFA has designated Dutch referee Danny Makkelie to take charge on Wednesday along with different assistant referees and a new fourth official.
