Folder Marker - Change folder color in two mouse clicks for easy at-a-glance identification.
MacOSicons.com - Free 5000+ macOS app icons in the style of macOS Monterey, Big Sur. Fully open source and community led. How to install custom icons on macOS Monterey, Big Sur.
Folder Painter - Folder Painter is an easy to use Portable Freeware program, which allows you to change the color of the icon representing a chosen folder to any color you like
Replacicon - Just updated to macOS Big Sur? You may have noticed some of the apps in your Dock look a bit inconsistent with the rest of the system.
Dr. Folder - Customize windows folder
IcoFX - IcoFX is an all-in-one solution for icon creation, extraction and editing.