How to change the swap the color of a shape within a texture?

I know next to nothing about shaders, so I'm not clear on how to do this. There is a single black shape on a white background. I want to change the color of the black shape and the color of the white background separately.

e.g. a black square on a white background could become a blue square on a red background

Is there an efficient way to do this?

to be clear I am talking about changing the colors of individual areas of a material

 

Is there a particular shader as a basis you were planning on using this with, i.e. Standard, Unlit, etc.

 

My knowledge of shaders is very limited, but unlit should be sufficient.

 

It should be as simple as modifying whatever shader you're using now to offset the resulting color.

For example if you're using the shader in this example named "Unlit/NewUnlitShader" https://docs.unity3d.com/Manual/SL-VertexFragmentShaderExamples.html

Then before "return col;" in the fragment shader you do something like:

col = fixed4(col.r + offset, col.g + offset, col.b + offset, col.a);

You probably want to do something different with the color channels than just add an offset but it's just an example.

If your shader does something more with the pixels than just read the color from a texture then you probably want to add your offset right after reading the color from the texture so that light calculations and other stuff happens after.

In the example above the line "fixed4 col = tex2D(_MainTex, i.uv);" is the line that reads the color from a texture.