Explanation of Fujifilm colour ethos and helpful visual graph of film simulations available in X cameras at Fujifilm X World's Facebook page.

“First of all, the color reproduction is not just a “tendency” for FUJIFILM cameras, but rather a “world of its own” to put it more correctly. It does not just look “vivid” or “soft”. They are in their own world of color reproduction of “Velvia” and “ASTIA”.
When you shoot a photo, you would first look at the subject. It can be anything from “autumn leaves” to “person”. And you would set it to “Vivid” or “Soft” depending on the subject. You may be happy with the result if the autumn leaves appear vivid or the skin appears soft.

At the same time, you may be unsatisfied with the result, but think that “it can be edited later” if they were shot in RAW.”

Source: The World of Film Simulation episode 1

via: Fujirumors. Thanks @umad.