To make sweet pepper relish, dice 3 peppers, boil them for five minutes and drain. In a saucepan, add 1/4 cup of vinegar, 1/3 cup of sugar, 1 teaspoon of salt, 1/4 teaspoon of celery seeds and 2 teaspoons of mustard seeds. Boil, add peppers and cook for 15 minutes.
To make hot pepper relish, pulse 1/2 pound of hot green peppers and 1/2 pound of hot red peppers in a food processor. Add 1/2 pound of yellow chopped onions, and continue pulsing until everything is evenly chopped. Put the mixture in a mesh strainer over a bowl, and stir in 1 tablespoon of Kosher salt. Let the mixture stand for three hours.
Rinse the mixture under cold water, and drain all the water. In a clean saucepan over high heat, add 1/2 cup of vinegar and 1/4 cup of white sugar, and bring it to a boil. Stir frequently to ensure that all the sugar is dissolved. Add the pepper mixture, and reduce the heat to medium-low. Let the relish simmer for 10 minutes, stirring occasionally.
Remove from heat, and let the relish cool for one hour. Pour the relish in an airtight jar, and refrigerate.
Use red peppers with the seeds for a hotter relish, or remove them for a sweeter taste.