In a large bowl combine the corn, red pepper, onion, and green pepper. Set aside.
In a large heavy bottomed pot, combine the vinegar, sugar, mustard seed, celery salt, crushed red pepper, and kosher salt. Over medium-high heat, bring to a boil and add the corn mixture. Reduce heat to low and simmer uncovered for 15 minutes.
After 15 minutes, scrape off any foam on top. Add the cornstarch slurry to the pot. Turn heat to medium and cook for an additional 4-5 minutes or until mixture begins to thicken.
Ladle into 4-5 sterilized pint jars. Leave 1/4 inch headspace and process in a water bath for 15 minutes. You can also refrigerate and use within a couple weeks.