What do these undocumented Style options in Mathematica do?

As mentioned in an earlier question, I have uncovered some style options that don't appear in the Mathematica documentation.

Style["This is a test", LineColor -> GrayLevel[0], 
FrontFaceColor -> GrayLevel[0], BackFaceColor -> GrayLevel[0], 
GraphicsColor -> GrayLevel[0], FontFamily -> "Arial", 
FontSize -> 20, FontColor -> GrayLevel[0]]

LineColor, FrontFaceColor, BackFaceColor and GraphicsColor aren't documented anywhere, show up in red when used in the front end, throw an error when used inside a Graphics 开发者_开发问答element and generally don't seem to have any function.

What are these options used for or why they turn up in this context?

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[per popular demand...]

The presence of these symbols is merely a leak of a front-end implementation detail into a user-visible structure. There's no reason for the average person to be interested in them. (I could probably count the set of people who should care about these options on one hand, and I'm not one of them.)