To Prepare Juice:
Wash peppers; remove stems and seeds. Cut peppers into 1/2-inch pieces.
Puree half the peppers and 3/4 cup vinegar in a food processor or blender. Puree remaining peppers and vinegar. Combine puree and apple juice in a large bowl. Cover and refrigerate overnight.
Strain pureed mixture through a damp jelly bag or several layers of cheesecloth. Measure 4 cups juice. Add additional apple juice if necessary, to make 4 cups.
To Make Jelly:
Combine juice, classic pectin and salt in a large saucepan. Bring to a boil over high heat, stirring constantly. Add sugar, stirring until dissolved. Return to a rolling boil. Boil hard 1 minute, stirring constantly. Remove from heat. Skim off foam if necessary. Stir in a few drops of food coloring, if desired.
Ladle hot jelly into hot jars, leaving 1/4 inch headspace. Adjust two-piece caps.
Process 10 minutes in a boiling water canner. Carefully remove jars from water using special tongs. Place on counter top and let sit 24 hours undisturbed.