They are made to coordinate with your overall flower theme and colour scheme, and can take many different flower types. You can also change the foliage to a rich dark green as well.
The long satin ribbons look beautiful as they float around in the breeze and also help to coordinate your colour theme.
A great way to mark the entrance to a ceremony room, church or wedding venue and can be used inside or out.
This photo is from
http://www.wedding-flowers-guide.com/wedding-ceremony-flowers.html