As a Roblox developer, fog does not have a LightInfluence property that would allow it to blend in with the game ambient, in which its absense prohibits it from properly blending in.
With the introduction of the LightInfluence property in SurfaceGuis, it has allowed SurfaceGuis to wonderfully blend in with the game lighting. Fog, which has been on Roblox longer than SurfaceGuis, is yet to have a LightInfluence property that would allow in-game lighting to influence its shade.
With this stated, I’d like to suggest that fog be given a LightInfluence property. It would allow fog to dynamically change in brightness when the time of day shifts from day to night; or to have a shade similar to the ambient color, should the ambient color change.