Color memory toy set

A color memory toy set, comprising:

• a color memory toy having a surface, at least one portion of said surface being provided with a color memory temperature-sensitive color changing layer colored with a coloring material comprising a color memory temperature-sensitive dye exhibiting hysteresis characteristics in response to temperature change between either (i) a colored state and a colorless state or (ii) a first color state and a second color state;
• and
• at least one simulated writing pen, said simulated writing pen comprising a pen body with a metal simulated writing tip end and a hollow pipe, wherein hot water as a heat medium or pieces of ice or cold water as a chilling medium can be freely inserted and removed therefrom so as to respectively form a hot-pen or a cold-pen thereby;
• wherein said hot-pen causes at least a part of an image to appear or disappear on said color memory temperature-sensitive layer by drawing an image on said layer whereby to change the color state of the drawn portion into a first state and said cold-pen causes at least a part of an image to appear or disappear on said color memory temperature-sensitive layer by drawing an image on said layer whereby to change the color state of the drawn portion to a second state.