In advance: Make fondant nails. Tint portion violet; reserve some white. Roll out 1/8 in. thick as needed. Cut 2 in. long tapered nails (1/2 in. wide at rounded bottom). Set lengthwise across cornstarch-dusted dowel rods; let dry overnight. Use royal icing to pipe tip 2 dot spider body and tip 1 dot eyes and outline web and legs. Outline and fill-in tip 2 icing face. For sugared nails, work with one color at a time. Brush on stripes with piping gel and sprinkle on sugar; let dry five to 10 minutes before applying next color. Let dry.
Prepare and tint dough. Press into cookie pan cavities. Bake and cool. Paint creases with mixture of vanilla and Leaf Green icing color. Attach nails with icing. Let dry.
* Combine Leaf Green with Lemon Yellow for green cookies.
* Combine Violet with Rose for violet shown.