John Zimmer, the cofounder and president of Lyft, was sitting in a meeting last week with his new chief marketing officer and one of the company's partners looking at data about the "ride-sharing" market. It should have been a fairly routine meeting, but for some reason, Zimmer had a big smile on his face.

"I said, 'Why are you smiling?'" says Kira Wampler, who took over as Lyft's CMO three weeks ago.

Zimmer's response, as she recalls it: 'When we first got going, we heard, 'This isn't ride-sharing, you can't call it 'ride-sharing.' You're a taxi substitute.' The fact that we are sitting here today with a major partner and that the word we are using is 'ride-sharing' is really enormous."

More than two years after founding Lyft, Zimmer doesn't need to argue as much about whether there is such a thing as a ride-sharing market. Investors have pumped billions of dollars into startups like his own that let users hail cars through apps and split fares with friends and strangers. Instead, the challenge that Lyft and its growing team face is how to define and brand itself within this fast-growing market.

"As its Goliath-esque competitor, Uber, has made several ethical lapses, customers are seeking a moral alternative, and Lyft seems to fit the bill," Nick Bilton wrote in a recent article for The New York Times. "But there’s a problem: Lyft’s cutesy branding is a major turnoff for those who may otherwise make the leap."

Bilton went on to list some eccentricities of the Lyft experience like the expectation to fist-bump drivers and sit in the front seat. And, of course, he touched on the big pink mustaches on Lyft vehicles that have become synonymous with the startup's brand. "No one wants to show up to a club or meeting, or to pick up a date, in a car with a pink mustache," Bilton wrote, "big or small."

Zimmer shrugged off the Times article in an earlier interview with Mashable as an issue publications are just interested in "given the competitive environment." That said, he's taking the underlying premise seriously enough: Lyft, he told us, is working to "mature and polish the brand experience."

As part of that effort to evolve its brand, Lyft brought on Wampler, who previously ran marketing at Trulia and Lytro before that. In a recent interview with Mashable, Wampler pushed back against the idea that the pink mustache and "cutesy branding" are bad things for Lyft.

"Many companies would kill for this kind of brand engagement: that there's so much passion about the mustache, and that it's pink, and what should you be doing about it," Wampler tells Mashable. "I can't tell you the number of companies that would kill for this kind of conversation."

And yet when asked whether the mustache will in fact be killed off, Wampler, like Zimmer when we spoke with him, stopped short of offering a firm denial.

"I don't have the final answer to is it forever, is it for two years, is it for two months," Wampler says. "I don't think either one of us are saying come hell or high water, to every car there will be a pink mustache. We understand that we are in a space of rapid disruption and pretty rapid evolution as a business... We reserve the right to make those decisions."

What Lyft has done so far is phase out the really big mustaches that are commonly seen in press photos (like the one above). "There's no big mustaches anymore," Zimmer told us in the earlier interview. "We stopped shipping those a couple months ago. All the press images that are out there, that's kind of part of our launch strategy."

In conversation, Lyft execs frequently refer to airline brands like Southwest and Virgin America as models for Lyft's branding strategy. Like Lyft, Wampler says these airlines succeeded with playful brands even as they dealt with fierce competition and regulatory issues. "The argument that you can't be a brand with a personality in order to compete is an argument that doesn't stand up," she says.

Far from being a liability, Lyft argues that personality — whether it be an optional fist bump or a driver who decorates their car with Christmas lights — is what helps set it apart from competitors like Uber.

"I believe they are looking at the world as an extremely efficient delivery system, whether what's being delivered is a person or a thing," Wampler says of Uber. "That is a fabulous way to win in a taxi-for-hire delivery part of the world, which we certainly have areas of overlap there. We are going after something much bigger and much different."

Uber, in her telling, is focused on delivery. Lyft, by comparison, is focused on convincing commuters, students and "the mom in the minivan on the way to the grocery store" to hail a ride instead. And to get those people, Lyft needs to emphasize its humanity. (For what it's worth, Uber would likely say it is targeting this use case as well).

"When your ethos is more delivery, then you end up with a much more efficient brand experience. There's no good or bad to that. It just is," she says. "In our world, because we believe very firmly in technology and humanity, you don't end up at the same place. And that's okay. There's more than enough room [in the market]."

The giant pink mustaches may not be here to stay, but Lyft's general quirkiness isn't going anywhere.