Opaline is a striping pattern mutation. It reverses the striping pattern on the head feathers so that there are thicker white areas and thinner black stripes. Another feature which adds to the beauty of this mutation is that the body feather color runs through the stripes on the back of the neck and down through the wing feathers. Opaline budgies' tails are characteristically patterned with light and colored areas running down the tail feather.

Basic Genetics:
Sex-linked (on the x-chromosome)
Details on opaline genetics...

The opaline variety has reversed markings on the head, compared to the normally striped budgie seen below.