Have a look at the dcolor submission to the file exchange. That should give you a good starting point for doing this.
There are all sorts of combinations to try to convey the complex-valued surface. You could put the angle as the colour for your surface and the magnitude as the z-value to the plain surf call
[x,y] = meshgrid(linspace(-2,2,1001));
z = log(exp(x).*(cos(y)+i*sin(y)));
, or the other way around, or the real and imaginary parts. When it comes to this type of plotting the best way is to try all sort of combinations you can imagine and see which works best for your purposes.