Plug colours and modern fuels

[MilesnMiles]

Seems when I check my plug colours these days I dint get the old familiar semi brown colour. My plugs whether taken out after idling or after a good thrash seem to be a vaguely greyish colour with a little soot around the first couple of threads. Porcelain is a dull white as it should be.
Do these modern fuels prevent plugs showing/taking colour as they used to.
Car runs without fault and shows mostly good AF number verging on the richer side except a leanish idle.