use of iPhones and iPads, citing concerns over “long-term health.” There’s also a growing movement among some early tech employees warning against the products they’ve built. And many consumers are starting to wonder what this is all doing to our minds.

Mack McKelvey, the chief executive of the marketing firm SalientMG in Washington, D.C., said she’s aware of the tricks phones use to keep you on them longer — and coming back sooner.

“You don’t buy black-and-white cereal boxes, you buy the really stimulating colored one, and these apps have developed really cool tiles, cool shapes, cool colors, all designed to stimulate you,” Ms. McKelvey said. “But there’s a vibrant world out there, and my phone shouldn’t be it.”

She decided to make the switch to gray as well. But it was tricker than she expected.

“It took like 40 minutes to figure it out. They buried the setting,” she said. “You have to really want to do it.” (If you want to try, here are some tips.)

One person Facebook and others turn to is Thomas Z. Ramsoy, the chief executive of Neurons, a four-year-old company based in Copenhagen. His business uses brain scans and eye tracking technology to study apps, updates and future technology. The company often measures the electrical activity of the brain while a consumer is interacting with a phone, such as texting and scrolling Facebook.

The goal, Mr. Ramsoy said, is usually for a product to inspire happy emotions and draw attention without freaking a consumer out. For the past year, he said, Facebook has been its largest client, publicizing some of the research. “There is so much business now, we pinch ourselves,” he said.

“Color and shape, these are the icebreakers when it comes to grabbing people’s attention, and attention is the new currency,” he said. “Having an interface that grabs people’s attention without disturbing them in the wrong way, without

consciously intruding in their space, that’s the line fine.”

Companies use colors to encourage subconscious decisions, Mr. Ramsoy said. (So that, for example, I may want to open email, but I’ll end up on Instagram, having seen its colorful button.) Making the phone gray eliminates that manipulation. Mr. Ramsoy said it reintroduces “controlled attention.”

“It’s a very good idea,” he said. “You have to take away the sound as well.”

One way Silicon Valley could help ease phone addiction is by using a more thoughtful color palette, said Bevil Conway, an investigator at the National Eye Institute, who researches color and emotion.

“Color’s not a signal for detecting objects, it’s actually something much more fundamental: it’s for telling us what’s likely to be important,” Mr. Conway said. “If you have lots of color and contrast then you’re under a constant state of attentional recruitment. Your attentional system is constantly going, ‘Look look look over here.’ ”

The same way people think about a color scheme when they’re planning the living room décor, Mr. Conway said, they should think about color when it comes to their phone’s home screen too.

“If you had a color pallette, you would end up with a phone that looked pleasant and was not addictively rewarding, that had some intentionality, but of course nobody wants you to do that,” he said. “Because what they want is for you to look.”