I am fortunate to have a room that receives late afternoon sunlight through the windows. They do however make unusual colours of quilts. The back of this quilt is White Magna Glide Classics 1900+ metre of it.
There are those shadows playing colours again. 9 different colours of Glide #40 and two of Glide 60wt used for the quilting.
I have Daylight lighting in my studio, plus 3 metres of windows on a northern wall. When you use your longarm table to sew on a hanging sleeve and for 3 random designs on the back the sleeve matched the facing.