When I was 14, I saved up money from my first web design job to trick out a really nice gaming PC. I outfitted my computer with tons of blue LED fans, and I kept it on at night, right next to my bed. Shortly after, I realized my sleep patterns were changing. While I wasn’t staying awake any later, it now took me longer to get to sleep. Was I eating differently? Was it just a part of being a teenager? Was it the light in my room? But the orange light from my ’80s era alarm clock wasn’t keeping me up. I finally determined that it must be the particular shade of blue light from my new computer. It took me some research to realize all this, but once I did, I started turning my computer off at night. Problem solved. And when I bought my next computer, I ordered fans with orange lights.

The bright blue light of flat, rectangular touch screens, fans, and displays may be appealing from an aesthetic perspective (more on that below), but from a health standpoint, it is fraught with problems. Blue light inhibits the production of melatonin, the hormone that regulates our sleep cycles. Blue light before bedtime can wreak havoc on our ability to fall asleep. Harvard researchers and their colleagues conducted an experiment comparing the effects of 6.5 hours of exposure to blue light, versus exposure to green light of comparable brightness. They found that blue light suppressed melatonin for about twice as long as the green light and shifted circadian rhythms by twice as much (3 hours compared with 1.5 hours). And worse, it’s been linked in recent studies to an increased risk of obesity and some cancers.

A decade after my experience with the LED fans, I started seeing blue displays everywhere. From mobile phones to in-car displays, blue lights were becoming the norm. It’s hard for me to think of any examples of prominent high-tech products on the market now without pale blue screens or indicator lights. LED-based bulbs with more blue light are fast replacing incandescent bulbs. The default display to our iPhones and Androids operates along the blue spectrum, as do our laptops; new cars, especially those like Tesla which aspire to be “futuristic,” come with blue-lit dashboard displays, and so do our “smart” appliances, televisions, video game consoles, watches–the list goes on.

Thanks to the rapid growth of connected devices and digitized appliances, blue light is now flooding into our lives in places where we’re most vulnerable. It’s why, for instance, when we stumble into the kitchen late at night for some water, we’re guided by the illumination from the touchscreen on our refrigerator–and the after-image of the screen leaves us half-blind, and once back in bed, half-awake.

The right color for dense information

It could be argued that the average person today manages as much information with their devices as an intelligence officer in a wartime situation. But from the Cold War up to now, the user experience of military and consumer technology has vastly differed: Airplane cockpits, submarines, and other military-grade systems are specifically designed for information density, with primary, secondary and tertiary information sources. A key difference in all of these interfaces is color–by and large, many military displays are deep red or orange.

Why use orange and red in military interfaces? They’re low-impact colors that are great for nighttime shifts. In addition, bright blue light is more likely to leave visual artifacts, especially in darkened environments. Have you ever been blinded by the display in your car–or on your phone–when you switch back and forth between looking at that screen and the road ahead? Because the screen is a brighter block of high-energy light, driving (or for that matter, walking) at night creates a longer, stronger afterimage that can adversely affect us when our eyes return to where we’re going.

BMW is a rare exception in the orange vs. blue design divide, because the car company follows the military’s reasoning: Since the ’70s, BMW has made its cars’ dashboard cluster lights with a red-orange hue, at a wavelength of 605 nanometers. This allows drivers to see the instruments clearly, the company found, while also enabling their vision to quickly adjust to the outside darkness after quickly glancing down; red-orange light also caused less eye fatigue.