The key to a successful image, he said, is working from the background to the foreground, constantly layering on the colors.
"You have to do the stage before you do the characters," he said.
Although Colombo's work is among the more visible pieces of iPhone art, thousands of people around the world use the $4.99 Brushes application to create digital images.
Steve Sprang, the application's developer estimates that, since he launched Brushes in August 2008, about 40,000 people around the world have downloaded the program.
The Mountain View, Calif.-based developer worked for Apple for seven years before striking out on his own.
"I've always been interested in computer graphics," he said, adding that he dabbles in art a bit himself. "When I was thinking about what to do when I left Apple, it seemed like a natural fit for the device. You're touching it, it seemed like a natural step to want to draw on it."
The intention, he said, was to create an application that would appeal to everyone but he hoped that working artists would find it valuable.
He said he's been very pleased by the response, pointing out that about 500 iPhone artists have posted the images they've created with his program on a Flickr Web site.
Stephane Kardos, a Los Angeles-based artist who is also an art director for the Walt Disney Co. (also the parent company of ABC News), was one of the first to use the program and has posted about 45 images of the Los Angeles area online.
Colombo said Kardos' sunset paintings partly inspired him to experiment with iPhone art.
Kardos's sketches are also done on site and take about 5 to 10 minutes to complete.
"The sunsets can be done even faster as the light is changing very quickly," he wrote.
Patricio Villarroel, a Paris-based artist, was also one of the first to download the Brushes application. Since 1996, he said he's been creating virtual paintings on his Mac. He migrated to the iPhone 2 weeks after Sprang launched Brushes.
But though professional artists have gravitated to the program, Colombo insists that iPhone art is for everyone.
"People should have fun," said Colombo. "It's good to do something that you can record your moments, create your own images. I still recommend people to play. I don't think play enough with pens and pencils and colors as much as they should."
ABC News' Wonbo Woo contributed to this report.