Combine cucumbers and salt in a large shallow bowl; cover and chill for about 90 minutes. Put cucumbers into a colander and rinse thoroughly under cold water.

Drain well, and return cucumbers to a bowl. Add the thinly sliced onion and peppers then toss with the cucumbers.

Combine the white sugar, white vinegar, apple cider vinegar, brown sugar, mustard seeds, celery seeds, and ground turmeric in a medium saucepan; bring to a simmer over medium heat, stirring until the sugar dissolves.

Pour the hot vinegar mixture over the cucumber mixture; let stand at room temperature for 1 hour.

Pour into equally into jars then cover and refrigerate for 24 hours before eating. Store in airtight jars in the refrigerator for up to 2 weeks.