Prerequisites

A link to the database:

https://github.com/lorandcompany/App-Color-Database

Explanation

This formula searches for the [notification's app package] and returns the colour that's linked to it. It returns a [custom colour], if the package is not in the database.

Code

$tc(reg, wg("<https://raw.githubusercontent.com/lorandcompany/App-Color-Database/main/colors.json>", json, ".[" + your_package_name + "]"), "^$", [custom color])$