How do I vary the color of a 3D scatter plot by it's location in the graph?

I'm trying to figure out how to replicate in MATLAB what another software does automatically(if I could find a way to attach a picture, I would). Essentially, I have a 3D scatter plot of about 2000 points, and I want the color of the points to vary based on on their position in the z-axis. I think there's a way to do it with colormap, but I haven't been able to figure it out. I also tried creating a series of if statements to create a vector C that would be equal in length to my x, y and z vectors and control the color, but I keep getting the following error message, and twice when I tried running the program like this, MATLAB has completely crashed on me:

Error using scatter3 (line 75) S must be a scalar or a vector the same length as X.

Error in Displacement (line 33) scatter3 (dis, DS{3}.y, DS{3}.x, C, S, 'fill')

Here's my code:

 dis = DS{ii}.r3
            l = size(dis)
            S = 10
            C = [ ]
           for i = 1:l(1)
                 x = DS{ii}.r3(i)
                if -2e-10<x<2e-10
                    C = [C; [0 1 0]]; %green
                elseif 2e-10<x<5e-10
                    C = [C; [1 1 0]]; %yellow
                elseif 5e-10<x<7.5e-10
                    C = [C; [1 0 0]]; %red
                elseif x>7.5e-10
                    C = [C; [1 0 1];];  %magenta
                elseif -5e-10<x<-2e-10
                    C = [C; [0 1 1]];  % cyan
                elseif -7.5e-10<x<-5e-10
                    C = [C; [0 0 1]];  %blue
                elseif x<-7.5e-10
                    C = [C; [0 0 0]];  %black
                else
                    C = [C; [0 1 0]];  %green
                end 

            end
            scatter3 (dis, DS{3}.y, DS{3}.x, C, S, 'fill')

            xlabel('Displacement')
            ylabel('x axis')
            zlabel('y axis')
            title(DS{ii}.d1)

Thanks!

JB