Stir together first 4 ingredients. Firmly press crumb mixture evenly on bottom and up sides of a 10-inch tart pan.
Bake crust at 350° for 7 to 9 minutes. Cool on wire rack.
Whisk together eggs, grated lime rind, and fresh lime juice in a non-aluminum saucepan over low heat. Add 1 cup sugar, 6 tablespoons melted butter, and if desired, food coloring; cook, whisking constantly, 8 minutes or until lime mixture is thickened and bubbly. Let cool 15 to 20 minutes.
Pour filling into prepared crust; cover and chill 4 hours or until set. Remove sides of tart pan, and garnish, if desired.