[Etoys] Pen color categoyry

[Yoshiki Ohshima]

> In Logo's Turtle, the pen was a tangible and visible entity which made it easy 
> for kids to comprehend it. In Etoy, the Pen is an invisible, abstract entity 
> whose presence is manifest only in the trails it leaves behind. This runs 
> counter to Morphic principle of directness. Instead, pen methods could be 
> factored into a separate Morph, say PenMorph, that can be manipulated by kids 
> directly to affect size, color, shape, trailstyle and up/down state.

  Yes, similar reasoning can go to the drawn trail as well.  There
were a few attempts to make the drawn line be a polygon.

-- Yoshiki