Considering the following BarChart :
How Could I adjust the Font for the Labeling Function as well as the Chart Labels ?
I tried nesting Style. Unsuccessfull.
BarChart[{1, 2, 3, 4},
ChartStyle -> {Blue, Red, Green, Yellow},
LabelStyle -> Directive[Black, Large],
ChartLabels -> {"COG1", "COG2", "COG3", "COG4"},
ImageSize -> {500, 300},
ChartBaseStyle -> EdgeForm[Thick],
LabelingFunction -> Bottom,
Background -> Black,
LabelStyle -> Directive[Black, Large]]

Do you mean something like this?
Edit
Change the style of the axes.