Popular “Notify with Color” Devices
First thing to note is that there are several different methods of color mapping, and different devices use different ones. This can make things a little complicated. A number of the specialty device type handers exist just to get better color mapping than would be available with the stock DTH.
Some of the most popular color changing devices are:
Hue bulbs connected to hue bridge
IKEA Tradfri bulbs connected directly to the ST hub
Osram/Sylvania bulbs connected directly to the ST hub
The Homeseer plug-in nightlight ( A combination motion sensor and nightlight with seven colors, popular for various notifications)
The Homeseer switch with indicator LEDs. This is a regular wall switch with a vertical line of tiny indicator LEDs which can each be set individually to different colors.
https://shop.homeseer.com/collections/lighting/products/hswd200
I don’t know whether the differences in color mapping for those devices affect your code at all or not, but I thought you would want to be aware of them since you may start to get questions from people using ADT tools once you add color features. 
Use Cases
- Households with young children or adults with cognitive issues may want to go with only a few color options, at least for the main devices. The most common are probably blinking red for fire or CO alerts (The ones where you need to get everybody out of the house), and blue or blinking blue for medical emergencies (the ones where you need to go to another Household member).
Quite a few security systems, including the ADT panel, have three panel types of alert calls to the monitoring center: fire, intrusion, and medical. I have seen people use red/yellow/blue for those.
- Lots of people do use color to indicate the security.mode as well, quite often light turned off to mean disarmed, light turned white to mean armed. I think that’s most common for people who are also using a red light for fire since kids or cognitively challenged adults might get confused if there were two different red light systems.
But there are lots of other variations for this. Some people use Off/Red, or white/red, or off/yellow/red if they want to distinguish between armed stay and armed away… i’m sure there are also some people who use green/red, I just haven’t seen that used as often.
- Then there are some people, particularly those using the Homeseer wall switch, who create very complex signaling systems because that device let you see seven different lights all at once. So if the third light down is red, it means there’s a motion in the garage. If the fifth light down is green, it means the pool pump is running. If the bottom most light is yellow, it means the side door is closed but unlocked. Etc.
Typically the only person who can remember what all of those mean is the person who set it up, but there are people who really like this option. So it’s good to know that the device exists and works well with smartthings. If anyone asks you “is there a way to see multiple status lights all at the same time, like a different light for each door?“ Then the homeseer wall switch is usually the answer.
- People with hearing challenges may also use multiple different kinds of light notifications, in many different highly individualized ways.
Summary
So, yes, I do you think there will be many people who would like a colored light notification for the security.mode.
There will also be many people who want The “alert with lights” setup Where specified colored lights come on to match one of the three types of emergencies: fire, intrusion, or medical. Some people also want a fourth one to distinguish between fire and carbon monoxide.
Finally, a small percentage of users want notifications which are specific to specific sensors. The “movement in the garage“ example. I think most people find those too complicated to keep track of, but there are people who really like to do that and there are definitely devices that can display the information.
Those are the main ones I can think of that would apply to the ADT model hub. Of course there are all kinds of other color notifications that people want for other purposes.