Are you sure you were rendering in the same mode as you were previewing?
depending on material type your results between fast mode and accurate mode could be very different.
otherwise what you see if what you should get, would you be able to post an example of what you are seeing?
I just installed 2018 Visualize and the image looks much better now. I'm not sure what I did wrong but the final rendering color seems to be lighter than what it appears on the 3D viewport
I used Pain to check the color and they are not the same
I'll use accurate mode to see what the result
thank you, JB