"The thing that took me totally by surprise was the spontaneity and happiness of the people," said Krishnan, 40, who attributed the traits to the uplifting power of Mandela's leadership.
"What Mandela instilled in the youth was the confidence that they can achieve: 'Believe in yourself. Don't worry about color.'
"They may have disagreements on other things. But when it came to Mandela," there was universal appreciation, Krishnan said.
So he consulted with the Mural Arts Program and decided the fastest route to a completed mural for his home would be a private commission.
Since Thursday, when word of Mandela's death at age 95 flashed across the world, the mural on Krishnan's wall has become an informal shrine. Some mourners have placed votive candles at its base.
An art buff with a passion for black-and-white photography, Krishnan said he was on the Internet using the search term "monochromatic" when the work of Ben Slow, a London painter with a streaky style called drip technique, caught his eye.
Slow, whose work includes a mural displayed at the Royal Albert Hall in London, does large-scale installations. Krishnan reached out to him. Without meeting in person, they refined the idea for the Mandela mural, based on a photograph and a projected budget of $5,000 to $10,000. Krishnan flew the artist in to do the work.
The mural, in dominant shades of red and black, is not a smiling Mandela, but "shows him deep in thought. With lines on his forehead," Krishnan said. "Showing the weight of his responsibility."
Using acrylic and oil-based media, Slow set up a workshop in Krishnan's South Philadelphia basement and painted onto aluminum panels of a type recommended by the Mural Arts Program. The program, Krishnan said, helped in many ways, including a referral to the company that supplied a cherry-picker to make it easier to install the panels.
Slow completed the work in 10 days, then spent three more installing it and adding brushstrokes to bring it to life.
"I've been informed that people have been gathering at the mural, which I think is amazing. But I can't say I ever thought about that when I was creating it," Slow said in an e-mail.
"I think it's important that such characters are remembered for what they did, as they gave up so much," the artist wrote. "I'm happy with the way it came out. Up to that point, the majority of my work had been in black and white. This was the first piece I painted on such a scale in color."
With one exception - a neighbor who thought she should have been consulted before the installation - Krishnan said the mural has been well-received.
Cindy Miller, 60, a dog walker in the neighborhood, said Monday that she passes the Mandela mural five days a week.
"I like it very much," she said, because he isn't, in her word, "Hallmarked" - reduced to a smiling stereotype.
"It doesn't whitewash him as a sweet old man," she said.
Inquirer staff writer Julie Zauzmer contributed to this article.