How to colour blend between two materials?

I’ve been trying to get a material (with an image texture) to animate towards a colour mix with transparency, but either I’m attempting something the wrong way, or unable to find the right keyword to find about similar examples.

What I’m trying to accomplish is to make a 3D character blush; I have the face area on it’s own material, with textures set, but that’s where my problem is. If it was animating between two colours, I would simply use Color.Lerp, but since textures are included, that makes me think I have to somehow have a colour mix option for this.

I’ve also tried to just use the built-in animator to see if Unity would blend between the colours of two different materials, but after all it turned out to be an instant change on the new keyframe; which leaves me to think so far my only exit could be to manually create several keyframes, and create several materials to get it close to acceptable.

Although my knowledge about it is close to zero, is this after all only possible with a custom fragment shader? I don’t know if there’s a suitable package, or built-in Unity feature that makes something like this possible, or if at all I’m approaching this problem the right way…

Update: This is the shader I’m using right now, from 魔王. It might be a little confusing since inputs are all abbreviated, so here are some example files that are being used.

Textures