As a Roblox developer, it is currently impossible to change much about the tool’s appearance in the hotbar. We can set the image and modify the color3 of that image in guis, decals, special effects like trails and such, but when it comes to the toolbar icon for a tool an image is all we can change.
I have a system that allows color variances of swords and weapons, and all UI accounts for it besides the tool tray. This is the only place where it’s inconsistent.
The backpack has no higher-privilege functionality. You can just modify it directly. I don’t think it’s a good idea to start adding APIs for little things like this when you could easily just make it yourself.
That requires knowing which things in the CoreGui and dependencies to copy over though as well as fixing any directory errors if there are any. Which can be confusing if you don’t know what you’re doing.
And I dunno we definitely should be having APIs to modify the CoreGuis more otherwise they wouldn’t be making efforts to make the chat more customizable.
And then it becomes the responsibility of the place author to keep their modified version up to date with the original if there are bugfixes, if API changes make it incompatible, or if new features are added and they want feature parity (and since the backpack is thought of as part of the platform, you will want feature parity for UX/consistency’s sake).
In an environment without version control software’s merging features.
So I’m not convinced making modified versions of CoreScripts is a very convenient path.
The chat isn’t a coregui anymore. The “efforts to make the chat more customizable” were putting it in a LocalScript, which is what I’m suggesting OP does with the backpack.