Legend specific values

data = {0.3, 0.3, 1.2, 0.8, 3.1, 1, 4, 0.1};

newdata = MapIndexed[If[# > Mean[data], Style[
	Legended[#, Row[{"bar", First[#2]}]], ColorData[63, First[#2]]], #]&, data];

styles = Sequence@@{ImageSize -> 400, ChartStyle -> Gray, GridLinesStyle -> Directive[AbsoluteThickness[3], LightGray]};

BarChart[newdata, ChartElementFunction -> "FadingRectangle", GridLines -> {None, {Mean[data]}}, Evaluate@styles, ChartLegends -> SwatchLegend[None, LegendMarkerSize -> 20, LegendMarkers -> "FadingRectangle", LabelStyle -> {Gray, Bold, 18}, LegendLabel -> "above mean"]]

-Graphics-