If the Agreement of Purchase and Sale or construction contract ("purchase agreement") included the right to select certain items of construction or finishing, such as colours and styles, these usually cannot be substituted without the purchaser's written consent.
In addition, if the purchase agreement states that the new home will include a particular item (such as a certain model of appliance, or a particular brand of window), but does not give the purchaser the right to make a selection, these items can only be substituted with items of equal or greater quality.