The Basilica of St Denis, Paris, France: South transept Rose window, subject: Jesse Tree (Ancestors of Christ). Art Nouveau style. WOW! What a window! Amazing colour--mauve, I think it is. Anyways, purplish blue. A deep, meditative colour, ideal for a mandala, which is what "rose windows" are, in effect.
The main aspect from that period is the architecture and from the architecture, two of the most impressionable things are the rose windows and the arch. Description from tripledart.blogspot.com. I searched for this on bing.com/images