If you sideload it should install as a separate instance with it's own settings etc. It works like this on Android TV, now you have me curious if it will work the same on my tablet(s).
If this colorized beta version breaks, switch over to the stable version. 
[Off to test on my tablet] [edit] <--- yes, sideloads as a 2nd instance when I transferred manually to tablet and installed, unsure how it installs from the utility mentioned at the top of the thread.
The play store version is separate from this side loaded version, neither touches the other. When there's an update, it installs over the older side loaded version and you continue on.
I mentioned that because of what happened last week. I got a new Shield Pro, installed play store version, then joined beta on Play Store. I figured it wouldn't co-exist in that manner, but I had to find out.
That was when I couldn't find the beta apk for sideload, turns out I'm blind.
So the reason they can both be installed despite being the same app is the directory naming structure that's used. They have different install paths if it's from the play store or sideloaded.
Is there an easy way to see what version of the Carbon Theme is running?
Yessir, go to settings, support, about
I'll start putting the current version in the original post again.
1.14.2354
3.20.310
5.19.29
Update to 6.22.2204
This is close to EOL. Sometimes I update it for myself and the few that use it. This last update took a while because of the SDK updates. I may do it for myself if I feel like it, but at this point, I don't mind the purple anymore, and am about ready to discontinue the project. If anyone would like to continue this project, please DM me so I can provide all my work with instructions.
Thanks!
Brian
I don't use fire sticks anymore since I'm all AppleTV now, but I really liked this, especially the transparent timeline. Thanks for sharing!
The transparent timeline and Quick Guide GUI, the things that come up during playback, I really wish they would make that standard in the normal app. That something i always found very annoying, how when i pause and want to see or read something on the screen, the timeline bar GUI covers it all up.
I too moved to Apple TV some time ago as my primary device. Still have 2x Nvidia Shields, that my mother uses, but she likes the purple.
7.6.2016
Anyone still using this, waiting for an update?
I've moved to all Apple TV viewing, so though I prefer the look of yours, I don't use this anymore.
Yeah I’ve mainly only got Apple TVs now.
Sold my shield but thanks for keeping it updated while I was using that.
@AtoZ0to9 theres no way to do this to the Apple TV app and sideload it, do you know?
Always wondered if it was the inability to edit the app or inability to easily install it that was the hurdle.
Still using it. Hopefully you can provide an update.
Nothing is impossible, I'm just so behind with the modding scene for Apple OS / apps, I've always just avoided their products. I honestly don't know what's involved with theming the app. For me to do it anyways. I suspect the developers could theme it quite easily. All I have is a locked down iPad Air I have gotten working with a tethered jailbreak on a few occasions. A big headache.
I'll get something thrown together shortly. If you'd like to hit me up on DM, I can provide my modded files to change the colors. That was the part that took the bulk of the work. Applying those edits to a new .apk is a less than 5minute process, so doing your own updates would be quite easy.
I'm using it on three Android devices since you came out with it 2 years ago. I upgrade from time to time and will enjoy the updates as long as you continue to provide them. 
Thank you.
Sideloading, is not a thing on Apple Ecosystem. At least for now. THIS may open the door to change that, but may only take effect in EU.
There are ways to get non App Store apps/software on Apple devices, mainly iOS, but it is complex and risky. Jailbreaking not as solid as it once was. tvOS is a different thing...