Changing an LED color at a certain time (time based visual alert)

I just recently changed my utility plan to one that charges much more for on peak vs off peak. Living in a house with roommates its a bit of a challenge to remind everyone of this, especially when I am not around. I figured however it should be possible to make a super simple, time based LED alert system. Place one of these little alert devices on power hungry appliances to make everyone more aware of their power use.

The design is simple, an arduino Beetle (small, cheap leonardo), a single WS2811 LED and a power supply. I know how to get the arduino to talk to the LED, however after doing some research I wasnt able figure out the best way to program the LED to change at certain times. I see that there is a "time" library but not sure how best to utilize that. Maybe someone has a good example of a project that does something at a certain time?

Once I can get this to work reliably I would love to release an instructible so other people can make this as well.

I would just kick em in the shin if they leave something on. That always works.... XD

Any ideas on this one? Aside from shin kicking :)

It's been more than ten days since I recommended kicking anyone in the shins so I have forgotten what the sensor is for this plan . Can you refresh my memory as to how you planned to sense devices being on ?

Let's try this another way...

Using the arduino "Time" library creating a program that at 10:00 change LED color to GREEN. The color will stay GREEN until 18:00, at that time the LED color should change to RED. then after 24:00 it repeats.

I know how to do the LED part of it (I have neo pixels and have used that library a fair amount) but the Time library I really don't have any experience with.

And perhaps there is an even easier way to do this?

The Time library is a software RTC. Additionally, it can be interfaced to a hardware RTC, but this is not required. As noted, without additional hardware, accuracy is dependent on the system clock.