legending – ‘PlotLegend’ does not display the correct symbol color


I am plotting some data points with a legend but PlotLegend does not yield the same color as the points have. Where is the mistake?

Here is the result that I obtain: (1): https://i.stack.imgur.com/s5yga.png

ListPlot({{0.4, 38}, {0.5,   15}, {0.6, 10}},
 Frame -> True,
 FrameLabel -> {"a", "b"},
 PlotMarkers -> {
   Graphics({EdgeForm(Directive(Thick, Blue)), White, Rectangle()},ImageSize -> (15))},
  PlotRange -> {{0.3, 0.7}, {0, 100}},
 PlotRangePadding -> {0.05, 2},
 PlotLegends -> 
  Placed(PointLegend({"data"}, LegendMarkerSize -> 14, 
    LabelStyle -> {FontSize -> 18, FontFamily -> "Arial", 
      Black}), {0.165, 0.215}))