How can I write a light shader that outputs the exact same color as defined by the scenes directional light?
The following simple script will not result in accurate colors.
shader_type spatial;
void light() {
DIFFUSE_LIGHT = LIGHT_COLOR;
}

The world environment has no background, ambient light or reflected light.

I am aware that LIGHT_COLOR is the light's color multiplied by the energy. But with the energy set to 1, I would expect it to be the same as the directional light's color.
Converting LIGHT_COLOR from linear to the sRGB color space does not help.