Now, having said that, there is SOME flexibility in what you get. For example, the first one shows roses in shades of pink but you can get other colors.
At some point in the planning process you will have a chance to talk to someone who can help you with floral design. It might be a good idea to have pictures of bouquets you like/want that you can email to them. They'll help you create a bouquet that is what you want.
If there's a lot of extras, there may be some extra charges. But changes like color usually don't cost extra.