Multi coloured web

Very cold outside this morning. The new water feature was frozen for the first time this year (note to self - must empty water feature and buy a protective cover for it, soon!)
Looked everywhere in the garden for a decent spider's web to photograph, but predictably there were none to be found. However there was one on the inside of the kitchen door. Not quite sure how I got this rainbow diffraction effect as I tried to reproduce it/improve it but couldn't.