One of the first smart home automations my wife truly appreciated wasn’t flashy. It didn’t involve a voice assistant or fancy touchscreen. It was just a single recessed light in the den that turned blue when the garage door was open—and went back to normal when it closed.

It solved a real problem. We had a habit of forgetting the garage door open. Sometimes it was cracked open overnight. Other times, it sat open for hours while we were upstairs or out running errands. It was an easy mistake, but one I wanted to fix with something subtle and visual—no buzzers or alerts.

The Hardware I Used

Here's the gear behind the automation. You don’t have to use the exact models—just something that performs the same roles:

• Garage Door Sensor: THIRDREALITY Zigbee Smart Garage Door Tilt Sensor — a reliable Zigbee tilt sensor mounted to the door itself.
• Smart Lighting: Philips Hue 5/6" Smart Recessed LED Downlights — I eventually swapped out all the den lights with these Hue bulbs, but only one changes color for this automation.
• Wall Control: Lutron Pico Remote — I hardwired the light circuit so it’s always powered, and used the Pico remote to control on/off while keeping smart control intact.

You just need:

• Something to tell when the garage door is open
• A color-capable smart bulb
• A way to integrate it into your lighting setup if you're using recessed fixtures

The Concept

The automation is designed to highlight the garage door's status without disrupting the room. So when the garage door opens, just one den light turns cyan. When the door closes, that light warms back up and shuts off—so it blends back into the room naturally.

Why It Had to Be Smart

At first, the basic part was easy:
Garage door opens → turn one bulb blue.

But I quickly realized the closing part was more complex. What if the den lights were already off? Or what if they were on at a warmer setting? If I just turned the blue light off, it would stay blue—and next time we turned on the room, one light would be noticeably off-color. That’s not acceptable in a space we use every night.

So, I created an automation that:

• Changes the bulb from blue back to a warm white
• Waits one second (so the state is stored in Hue or Home Assistant)
• Then turns it off

This way, it blends back in the next time we turn on the den lights.

Creating This in Home Assistant Using the UI

You can build this easily without touching any code. Here's how:

1. Add a New Automation

In Home Assistant, go to Settings → Automations → + Create Automation, then start from an empty automation.

Name:
Sync Den Light 4 with Garage Door

2. Add Triggers

Add two triggers using the Garage Door Tilt Sensor:

Garage Door Opens

• Trigger type: State
• Entity: binary_sensor.garage_door_status_sensor
• From: off
• To: on

Garage Door Closes

• Trigger type: State
• Entity: binary_sensor.garage_door_status_sensor
• From: on
• To: off

3. Add Actions

Use a Choose action block to define two paths:

If the garage door is open:

Condition (template):
{{ trigger.to_state.state == 'on' }}

Action:

• Service: Light turn on
• Entity: light.signify_netherlands_b_v_lcd006
• Set color to cyan (RGB: 0, 253, 255)
• Set brightness to 70%

If the garage door is closed:

Condition (template):
{{ trigger.to_state.state == 'off' }}

Actions:

1. Turn light on with:
   • Warm white (color temperature: 3200K)
   • Brightness: 70%
2. Wait 1 second
3. Turn the light off

4. Set the Mode

Set the automation mode to: Single

Why It Works So Well

This is one of those automations that just makes sense. There are no notifications, no sounds—just a subtle cue in the room you’re already in. If there’s a soft blue light glowing in the den, the garage is open. And when it turns off, you know everything’s secure.

It’s so effective and non-disruptive that it’s become my wife’s favorite automation in the house.