The 'blue essential oils' contain the chemical constituent: 'Chamazulene'.
Chamazulene is a powerful antioxidant. It inhibited lipid peroxidation in a concentration and time dependent manner. No toxicity data for chamazulene.
A deep blue oil extracted from the chamomile flower. It is a "natural" anti-inflammatory agent used in herbal remedies and cosmetic products.
Great Article written by Eva Marie Lind: Azulene and Chamomile
ref: Essential Oil Safety by Robert Tisserand / Rodney Young