How to mix pixel colors in Shader?

Question

I have a pixel that have a colour RGB. This color is calculated by the shader and can be anything.

How can I override this color by a colour I choose. If my pixel is white it's simple, I can do this:

half3 original = half3(1, 1, 1);
half3 mycolor = half3(1, 0, 0);
half3 result = original * mycolor;

But what can I do if:

half3 original = half3(0.36, 0.74, 0.18);
half3 mycolor = half3(1, 0, 0);
half3 result = ?;

What operation or function should I apply to my original pixel color to override it ?

Answer 1

It was very easy finally. Here is the answer. I am using an external value.

half3 original = half3(0.36, 0.74, 0.18);
half3 mycolor = half3(1, 0, 0);
half value = 0.5;
half3 result = original * value + mycolor * (1 - value);

You could also use mix(); or lerp(); depending on your platform.

Answer 2

Just

half3 result = (original + mycolor) / 2;

does what you'd expect because the arithmetic operators are overridden for the half3 type.