Suppose I want contour plot of $x^2-y^2$, for $x,y\in[0,1]$ (my actual function is more complicated). Over this interval, $x^2-y^2$ is sometimes positive and sometimes negative. Using
ContourPlot I get all the contours, negative as well as positive.
But what if I wanted only those contours with values $\geq 0$ to show, while those contours whose value is less than zero are not displayed or (worst case) shown by the same color (say white). I doubt if this is possible at all, but any help is much appreciated.