Red or amber light is the best choice for sleep. These long-wavelength colors have the least impact on your body’s melatonin production, the hormone that signals it’s time to sleep. Blue and bright white light, on the other hand, actively suppress melatonin and keep your brain in daytime mode, even at relatively low brightness levels.
Why Blue Light Disrupts Sleep
Your eyes contain specialized light-sensing cells called photosensitive retinal ganglion cells. Unlike the cells that help you see shapes and colors, these cells exist specifically to tell your brain whether it’s day or night. They’re most sensitive to short-wavelength blue light at around 480 nanometers, which is abundant in sunlight, LED screens, and cool white bulbs.
When these cells detect blue light, they suppress melatonin production and directly increase alertness. Research on circadian biology has confirmed that blue light both resets the body’s internal clock and enhances wakefulness compared to longer-wavelength light. This is exactly what you want during the day. At night, it’s the opposite of what your body needs.
White light causes problems too, because standard white LEDs and fluorescent bulbs contain a strong blue component in their spectrum. Exposure to white light at night suppresses melatonin, disrupts circadian rhythms, and contributes to poorer sleep quality overall.
Why Red and Amber Light Work Best
Red light sits at the opposite end of the visible spectrum from blue, with wavelengths around 620 to 700 nanometers. Those specialized light-sensing cells in your eyes respond only minimally to red light. This means a red or amber light source lets your melatonin rise naturally in the evening, closely mimicking what happens in darkness.
Studies comparing blue and red light exposure at night have found that melatonin levels remain significantly higher under red light, similar to levels seen in complete darkness. Amber light (roughly 590 nanometers) falls close to red on the spectrum and offers a similar advantage, with a slightly warmer, more natural-looking glow that many people prefer for evening lighting.
If you don’t have a red or amber bulb, a warm white light labeled around 2700K (the “color temperature” printed on the box) is a reasonable backup, as long as you keep it dim. It still contains some blue wavelengths, so it’s not as effective as true red or amber, but it’s far better than standard or cool white lighting.
How Dim Your Evening Lighting Should Be
Color matters, but brightness matters just as much. Even a warm-toned light can interfere with sleep if it’s too bright. The WELL Building Standard, a set of evidence-based health guidelines for indoor environments, recommends that bedroom lighting at night stay below 50 equivalent melanopic lux, measured at about 30 inches above the floor. In practical terms, that means noticeably dim, enough to move around safely but not enough to comfortably read a book.
A simple test: stand across the room from your light source. If you can clearly make out fine details on objects, the light is probably too bright. You want just enough to navigate without bumping into things.
Night Shift and Blue Light Filters Fall Short
If you’re relying on your phone or tablet’s built-in night mode to protect your sleep, the news isn’t great. A study examining Apple’s Night Shift feature found that melatonin suppression did not significantly differ between Night Shift settings. Changing the color tone of a screen without also reducing its overall brightness appears to be insufficient for preventing melatonin suppression.
The core issue is that these filters shift the screen’s color slightly warmer but leave enough short-wavelength light and overall intensity to still trigger those light-sensitive cells. If you use screens before bed, dimming the brightness to its lowest setting alongside the color filter helps more than the filter alone. Better still, switch to a non-screen activity in the last hour before sleep.
Setting Up Your Bedroom
The simplest approach is to swap out your bedside lamp bulb for a low-wattage red or amber LED bulb. These are widely available and inexpensive. Use it as your only light source during the hour or two before bed. Overhead lights, even warm-toned ones, tend to be too bright and too close to your eyes. A single dim lamp at or below eye level is ideal.
For hallways and bathrooms you might visit during the night, plug-in amber night lights positioned near the floor work well. Floor-level placement keeps the light diffuse and out of your direct line of sight, reducing the chance of a middle-of-the-night bathroom trip resetting your alertness.
Night Lights for Kids
The same principles apply to children’s rooms. A dim red or amber night light is the best option for toddlers and young children who need some light for comfort or safety. Blue-toned and bright white night lights send an “it’s still daytime” signal that can delay sleep onset and cause more frequent waking.
Place the night light near the floor and away from the crib or bed to reduce direct exposure to your child’s eyes. Choose the lowest brightness setting available. If red or amber isn’t an option, a warm white bulb around 2700K on its dimmest setting is an acceptable alternative.
Quick Color Guide
- Red (620–700 nm): Best for sleep. Minimal melatonin suppression. Ideal for bedside lamps and night lights.
- Amber/orange (590–620 nm): Nearly as effective as red, with a more natural look many people prefer.
- Warm white (2700K): Acceptable if kept very dim. Still contains some blue wavelengths.
- Cool white (4000K+): High blue content. Avoid in the evening.
- Blue (450–490 nm): Worst for sleep. Directly suppresses melatonin and increases alertness.