777 Blue Light on side of seats
 

Dear FT,

I flew on a CO 777 TLV-EWR the other day and was sitting in an aisle seat. When I looked down the aisle I noticed a few aisle seats had a small blue dot lit up. What is this small light. Every aisle seat had the light but only a few were lit. Thanks in advance.

The blue light turns on when the AC power in that row is in use.

AC Power
 

Why do they have these in use? What is the purpose of those blue lights...who needs to know about who is using power?

Just a guess - it can show the FA's who is using electronic equipment when it's not supposed to be used (i.e takeoff and landing).

There enabled (blue) with the Captain turns off the sterile cockpit light 10,000 ft MSL and turned off (red) when the Captain turns on the sterile cockpit light 10,000 ft MSL.

This rationale doesn't make sense -- the power is disabled for takeoff and landing, so it shouldn't matter.
That said, I've never noticed a blue light. Is it only in coach? The OP wasn't clear. If so, that's why I've never noticed it. :D

Blue lights on A330's also
 

I just noticed that for the first time also on a NW flight from HKG to NRT.

I thought it was strange that after taking 100's of flights on 777s and A330's to just notice that blue light for the first time?

No, they are on the BF seats too.. I thought they were green, tho. lol

Can't speak for any other airlines but at CAL the following applies. I guess the colors are blue and red so the F/A's can look and see if the power to the plug outlets has been turned on/off, or to remind the pilots to turn on or off the sterile cockpit light.

We turn the sterile cockpit light on during our after start check list and turn it off climbing through 10,000 ft MSL and back on descending on through 10,000 ft MSL.

Aren't you talking about the lights on the ceiling by the doors rather than the lights on the side of each row of seats?

Nope. Blue lights on the seats power on to the outlets and Red lights power off to the outlets are hot wired to the sterile cockpit switch on at least all B757's and B767's at Continental if not the whole fleet. They also turn on the blue light outside the cockpit door (primary reason for switch) to indicate to the F/A's the cockpit is honoring sterile cockpit rules per FAR's and company policy.

I guess the company felt this is a good way to make sure the outlets are turned off during take off and landing since marrying it to the sterile cockpit light switch which will also be turned on and off during the exact same time periods.

Should there be some sort of mishap with someones electronic device then the blue light indicates that it is or is not receiving power from the outlet.

May affect how to handle the situation.

K Mart ?

It means you put the duty free on 50% off? nice!

That's interesting to know!

FWIW, there are also similar blue lights on the seats of 737 aircraft with in-seat power.