*.Colors.FocusedSelectionBorderColor := ...;
        *.Colors.UnfocusedSelectionBorderColor := ...;
        *.Colors.FocusedSelectionColor := ...;
        *.Colors.UnfocusedSelectionColor := ...;

procedure TBaseTreeFrame.VSTBeforeCellPaint(Sender: TBaseVirtualTree;
  TargetCanvas: TCanvas; Node: PVirtualNode; Column: TColumnIndex;
  CellRect: TRect);
var
  SelColor, InactiveSelColor: TColor;
begin
  if BusinessDataModule.Parameters.bExpertParams.SelColor = clDefault then
    SelColor := DarkenedColor(TargetCanvas.Brush.Color, 30)
  else
    SelColor := BusinessDataModule.Parameters.bExpertParams.SelColor;
  InactiveSelColor := BrightenedColorProp(SelColor, 128);

  if Column >= VST.Header.Columns.Count then
    Exit;

  if VST.Selected[Node] or (VST.FocusedNode = Node) then
  begin
    if VST.Focused or VST.IsEditing then begin
      TargetCanvas.Brush.Color := SelColor;
    end else begin
      TargetCanvas.Brush.Color := InactiveSelColor;
    end;

    if (Column = VST.FocusedColumn) then begin
      if (Node = VST.FocusedNode) then begin
        if IsCellEditable(Node, Column) then begin
          if IsObservableRed(SelColor) then begin
            VST.Colors.FocusedSelectionBorderColor := clRed;
            VST.Colors.UnfocusedSelectionBorderColor := clRed;
          end else begin
            VST.Colors.FocusedSelectionBorderColor := clWhite;
            VST.Colors.UnfocusedSelectionBorderColor := clWhite;
          end;
        end else begin
          if IsObservableYellow(SelColor) then begin
            VST.Colors.FocusedSelectionBorderColor := clYellow;
            VST.Colors.UnfocusedSelectionBorderColor := clYellow;
          end else begin
            VST.Colors.FocusedSelectionBorderColor := clOlive;
            VST.Colors.UnfocusedSelectionBorderColor := clOlive;
          end;
        end;
        VST.Colors.FocusedSelectionColor := DarkenedColor(SelColor, 15);
        VST.Colors.UnfocusedSelectionColor := DarkenedColor(InactiveSelColor, 15);
      end else begin
        VST.Colors.FocusedSelectionBorderColor := SelColor;
        VST.Colors.UnfocusedSelectionBorderColor := InactiveSelColor;
        VST.Colors.FocusedSelectionColor := SelColor;
        VST.Colors.UnfocusedSelectionColor := InactiveSelColor;
      end;
    end;
  end;
  if TargetCanvas.Brush.Color <> VST.Color then
    TargetCanvas.FillRect(CellRect);
end;