function valueToColor(aValue: double): TAlphaColor;
  var
    tmpSingle: Single;
    tmpAlphaColor: TAlphaColor;
  begin
    // 割合を0.15 なら1とするように切り上げる
    tmpSingle := aValue * (1/0.15);
    if tmpSingle > 1 then tmpSingle := 1;
    // 最大値 160（青） 最小値 0（赤）に補正
    tmpSingle := tmpSingle * 220 / 360;
    tmpAlphaColor := HSLtoRGB(tmpSingle, 0.75,0.5);

    tmpAlphaColorRec.Color := tmpAlphaColor;

    result := MakeColor(tmpAlphaColorRec.R,
                        tmpAlphaColorRec.G,
                        tmpAlphaColorRec.B,
                        $80);
  end;