These fringes formed in a water drop on a spider web look unusual because the outer edge is blue when it would normally be red.
Right; Moving more into focus to identify the source.
Left; Closing in on the drop at the intersection of horizontal and vertical strands.
Right; The closeup view of the drop shows the source of the fringes is in an area of changing curvature.
It looks like the water drop is acting as a negative lens at this point which reverses the dispersion.
Canon EOS 20D 20th September 2008
Wiltshire, England