Understanding first premise using preferential order

[kartik vermun]

I am trying to understand the first premise. 

Let's say I have various shapes of various colors. 

shape.shape_color(circle,red)

shape.shape_color(circle,green)

shape.shape_color(circle,blue)

and I have a preferential order = ['blue','green','red']

So i want circle , blue as the final shape color pair.

I have the following rule - 

select_shape_colors

    foreach

        shape.shape_color($shape,$color)

    $color_preference = get_color_preference()

    forall $color in color_preference

        first

            shape.shape_color($shape2,$color2)

    assert

        shape.final_shape_color($shape2,$color2)

fc_extras

    def get_color_preference():

        return ('blue','green','red')

I an unable to figure out the errors in this rule, be it syntax or logical.

Does anyone have any idea?

Thanks