Hello world in OpenSCAD

cubes.scad

$cubeSize=10;
$cubeCountX=3;
$cubeCountY=3;
$cubeCountZ=5;

for(x = [1:1:$cubeCountX])
    for(y = [1:1:$cubeCountY])
        for(z = [1:1:$cubeCountZ])
            color([x / $cubeCountX, y / $cubeCountY, z / $cubeCountZ])
            translate([x * $cubeSize, y * $cubeSize, z * $cubeSize])
                cube([$cubeSize, $cubeSize, $cubeSize]);

* color("red")
    cube([$cubeSize, $cubeSize, $cubeSize]);

* color("blue")
    translate([0,0,$cubeSize])
        cube([$cubeSize,$cubeSize,$cubeSize]);