Can a colander (utensil with holes) be used on shabbos to wash fruit and vegetables?
Answer:
If the colander is only being used to hold the fruit, and to allow the water to pass through, this will not involve a prohibition of borer.
The possible problem of borer in washing fruit involves the dirt that it "mixed" with the fruit. Once the water takes off the dirt, there is no longer a "mixture" of fruit and dirt, and therefore there is no problem of the water passing through (with the dirt) the holes of the colander.
Best wishes.