Pedro Julio Serrano with a rainbow Puerto Rico flag before the parade on Sunday. View Full Caption Courtesy Pedro Julio Serrano

ASTORIA — A Queens car company tasked with driving participants of the Puerto Rican Day Parade through the route on Sunday refused to transport a gay honoree because he was carrying a rainbow flag, organizers said.

The Custom Shop, a car customization company based in Astoria, volunteered five of its Jeeps to drive honorees along the Fifth Avenue parade route in Manhattan, including LGBT and human rights activist Pedro Julio Serrano.

But the company took issue with Serrano and fellow marchers as they were getting ready to hop in one of the cars with rainbow pride flags in tow, the activist told DNAinfo on Tuesday.

"One of them saw my rainbow flag, and they said that they didn't want their vehicles associated" with the gay pride symbol, said Serrano, who denounced the company in an emotional video posted to his Facebook page.

He said he was told by the company that he could ride in the car if he ditched the rainbow flag — something he promptly refused to do.

"I'm not going to let any one of my identities be left behind," he said.

Ululy Martinez, vice chair of operations for the National Puerto Rican Day Parade's board, said someone from the The Custom Shop — he believes it was the company's owner — said the flags "would undermine the image of his business."

"They were very clear that he didn't want to accommodate [Serrano] with the LGBT pride flags," Martinez said. "It was really unfortunate, because it was a day when we were recognizing the accomplishments of the LGBT community in Puerto Rico and in the United States, and discrimination reared its ugly head."

The Custom Shop did not return calls and emails seeking comment Tuesday.

After a terse exchange, The Custom Shop and its cars left, according to Serrano. He and the other honorees who were slated to ride in the company's Jeeps walked the length of the parade on foot instead, he said.

"We said, you know what we're going to march — we don't care about the cars," Serrano said.

The incident was particularly stinging, he said, as it took place the same day as the deadly shooting in Orlando, Florida, when a gunman killed 49 people after opening fire in a gay nightclub there.

"It happened hours after we found out about the tragedy in Orlando," Serrano said, saying he and other members of the local LGBT community were still "dealing with the enormity" of the massacre. "We were feeling this devastating loss."

Serrano — who is now currently in Orlando — says he plans to file a complaint against The Custom Shop later this week with the city's Commission on Human Rights.