Sintara can't be Shreever, since her serpent name is stated to have been Sisarqua (did I spell that correct?). She Who Rembers has not survived the journey.

I had forgotten that the name Sisarqua was mentioned and that SWR did actually die on the river - I have to add it to the wiki right away. Thanks!

I am pretty sure that Kalo is Kelaro, from his size, attitude and extremely similar name! If so, his colour has changed from "cobalt" to "blue-black" but that is not much of a change and it seems clear that colour changes can occur during dragon metamorphoses