In a medium saucepot, bring the vinegar, water, sugar, kosher salt and turmeric to a boil over medium-high heat.
Reduce the heat to medium-low and simmer until the sugar is dissolved.
Meanwhile, in a mixing bowl, combine the cucumbers, onion, red bell pepper and yellow pepper, tossing until combined.
Stir the chopped vegetables into the saucepot and return to a boil.
Reduce the heat to medium-low and simmer for 15 minutes or until the vegetables are tender-crisp.
Using a slotted spoon, carefully transfer the vegetable mixture into two mason jars (12 ounces each). Add the liquid just up to the base of the rims of the jars, discarding any extra liquid.
Let stand, uncovered, until the mixture comes to room temperature, about 1 hour.
Seal and refrigerate for at least 8 hours or overnight.
To serve, using a slotted spoon, transfer the relish to a serving bowl. You can also serve the relish directly from the mason jars but serve it with a slotted spoon.