I've got a range - albeit a WIDE range - for Slate Black eyes:
Kitten 1 has Morning Glory eyes, so Eloy must hide Morning Glory or more recessive:
Kitten 2 has Slate Black, which makes that Eloy's hidden eye:
Her mom, Edna, has Destiny Waters and hides Grey Matter. (I will post the proof of her hidden Grey Matter if needed, it will take a few generations, so won't post it all here.)
Therefore, since Eloy passed his hidden Slate Black both times, and it hid behind Morning Glory in Kitten 1, Slate Black is recessive to Morning Glory and dominant to at least Grey Matter and possibly to Destiny Waters. Oriana's testing of her kitten could narrow that range considerably.