The distance between two points can be determined using the Pythagorean theorem.
d = sqrt((x2-x1)^2+(y2-y1)^2+(z2-z1)^2);
In order to set colors you can use logic indexing.
color = cell(size(d));
color{d<10} = 'blue';
color{d>=10&d<20} = 'green';
... % Other colors
If you're wanting to actually set the colors in a plot, then just look up the color codes and set them accordingly.
