That certainly shouldn't be the case, especially if the pool water is correctly balanced at the time of closing the pool then there is no reason for it to be green when it is opened. Even if it is green it only needs three or four days to get it back to clear so there is no need to change the water. When we open a pool we want to be certain it is ready for you to dive straight in without any remedial work having to be done.
To ensure this is the case we visit the pool on a regular basis (free of charge) throughout the closed season to check the cover is still in place and to check the water chemistry is still correct and adjusted if required. By doing this we don’t get any nasty surprises when we open the pool, there is no extra work that needs to be done before your season starts, no extra costs to the owner and we can move straight into the weekly maintenance routine.
As they say, prevention is better than cure.