Legend-Specific Values 

In[1]:=

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

In[2]:=

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

Modify the data to add a unique color and legend text for elements in the data that are larger than the mean.

In[3]:=

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

Create a bar chart that legends the elements that are larger than the mean.

In[4]:=

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

Out[4]=