Are Saffron Crocus petals edible?
It seems that the answer is yes... 

The vast majority of the literature out there around saffron petals relates to the pharmacological compounds found in the petals. For normal use, the petals are considered a "waste" product from the production of saffron in the forms of the well known stamens used in food flavoring and coloring.

However, I have found that petals contain less of the flavoring and coloring compounds, but still contain some and are sometimes used as an adulterant (see Substitutes and Adulterants section near the bottom) in the commercially produced stamens. I also found a book Saffron production and processing, which states (see linked page 8 of chapter 1) that the petals could be used to generate natural colorings for foods, particularly anthocyanines.