ALTX is an editor extension for easy texture adjustment
(also useful for creating prebuilt texture color variations).

This extension does not create additional files. It uses Unity Scripting API to store adjustment settings in Unity's meta-files. The original texture files in the project folder are not changed. This extension adjusts the textures just before the Unity Editor compresses and stores them in the cache directory. Imported textures will be adjusted and the original texture files will not be changed. You can change import settings or export and import the packages, adjustments will not disappear.