Not sure if this has been mentioned yet in this thread, but for 2013 there will be the "new" Bleu de Galice.
For those of us, who more or less often can't tell Bleu Electrique apart from Bleu Hydra and Cobalt, this will be just a new addition to the confusion
bring it on...
As per Bleu Hydra, it is nothing like Mykonos to me. Mykonos is a real deep turquoise, closer to the Bleu Azteque. Hydra is more blue (cold), like a real true intense blue, very similar to Bleu Electrique, but less "screaming", if I make any sense here.
Bleu Lin has got some gray undertones, which makes me personally prefer it much more over Ciel or Celeste, as these were too tender- boring- baby blues IMHO.
Bleu De Galice, to me, is a more intense Blue Thalassa. Definitely the same color family. It is lighter, brighter and it does have less teal, green undertones, than BT.
Hope this helps