Question Modify Standard Shader or New Shader With Second UV Channel

I am working on a project which needs a special shader. I dont know how to write shaders and searched for possible solutions but couldnt find any proper solution.

I have a car model wtih 2 different uv maps and using standard shader on it. I want to use albedo texture and decals texture in this shader. Standard shader has a property named "UV Set" for second uv channel. It is working like I want but except color because when I change the albedo color, also decals texture getting colored.

How can I modify the shader to not colorize the decals texture (secondary map in standard shader) ?

or

How can I write a shader with mainTex,decalTex,color properties but decal texture should be in second uv channel and not affected by color?

Thanks

 

You'll need to write yourself a custom Surface Shader.
https://www.alanzucconi.com/2015/06/10/a-gentle-introduction-to-shaders-in-unity3d/