List Contour plot

My data for List Contour plot ranges from -30 to 2500. The contour plot i am getting fails to distinguish the highest or the lowest ranges. How can i make it plot all the values with a colour?
This is my input for now:

ListContourPlot[Pes, ContourLabels -> All, PlotLegends -> Automatic, 
ColorFunctionScaling -> False, PlotRange -> {{0, 180}, {6, 8}}, 
ColorFunction -> Function[{Enn}, ColorData[{"BlueGreenYellow", {0, 300}}][Enn]], 
FrameLabel -> {{HoldForm[Intermolecular distance (cm - 1)], 
None}, {HoldForm[Angle degrees], None}},PlotLabel -> HoldForm[Triplet state F12b], 
LabelStyle -> {GrayLevel[0]}]