The phrase "fine colander" refers to a kitchen tool that is used to strain or drain liquids from food. It has small holes which allow fine particles to be separated, leaving behind the larger pieces. Full definition
Line a large sieve, or fine colander with cheesecloth (or double layer of damp paper towels) and pour the broth through the sieve / colander into another pot. (howtofeedaloon.com)
Cut up the cauliflower a bit, pop in the blender, fill with water up to the top of the cauliflower, blend and then put it through a fine colander. (theironyou.com)