Rendering gradient UVW under a dome light

Hallo dear community, I have 2 question about the Dome-Light in the new V-Ray 5.

I need to render a Vertex-surfaces (UVW) with gradient color, and I need to keep the original coloring of the gradient.
Could tell me which setting allows me to have the original coloring?
Set the EV to 10 and mantain a low light intensity, I can get close, but not 100%.

Another question is whether is possible to prevent certain surfaces from being affected by the active shadow of the dome light or by the ambient occlusion, because in both cases, altered the color of the gradient, making it darker.

any advice will be very important.
Best regards