I usually skip feeding my corns if they're in blue also, even though some will take food anyway. And I agree, feeding does not need to be "exact"...if you have a snake
that's had trouble gaining weight, feed a little more...but usually it's the opposite problem, "more appetite than actual food needed". Corn snakes make great pets in
part because they're so easy to get along with...they usually have a great appetite & take f/t prey easily, & on top of that, they're quite pretty.