The Zephelium, the original race line of the modern Zeta Reticuli and their Greys, were one of the visiting groups to Atlantis who became genetically mixed with some of the Templar-Annu race families.

The reason contemporary Zeta sought genetic material from our race was that they hoped to find traces of their own original genetic imprint in our DNA, so they could reverse the mutations that had occurred in their own genetic lines and create hybrid versions of themselves more suited to Earth's environment.

The blue-skinned Zephelium are the administrators caste of the Zeta, governing all lower-rank Zeta castes.

(Voyagers I – Page 8)