See if this does what you want:
[X,Y] = meshgrid(-10:10);
Z = X.^2 + 0.1*Y.^3; % Create Data
figure(1)
contourf(X, Y, Z, [min(Z(:)); 10]) % Use The ‘10’ Contour As The Cutoff
colormap([1,0,0; 0,1,0]) % Define Colours In ‘colormap’
figure(2)
surf(X, Y, Z)
grid on
colormap([1,0,0; 0,1,0])
The surf plot is there simply to demonstrate that the contourf call does what you want. The surf plot does not use a specific cutoff. See the documentation for contourf for a full description of how this particular call to it works.
