SpriteMask effect but with MeshRenderer o UI element

Hi!
I am faced with a problem.
I have a character, who colors himself. I have an animation of the character without color and with color.
Well, what I want to do is a "window", to show how the character is gradually colored.
The program I use for the export of my animations (DragonBonesPro) can export as Mesh Renderer or as UI Element (with a rect Transform).
I was wondering if there would be any way to achieve the SpriteMask effect but using one of the two things above. What I have found is that I need to use shaders, but I have no idea how they work, create or use them.

If someone helps me I would be very grateful!!

PS: I'm in 2D.