What do you think of my cute brother/sister combo?

Alone, I like all the names (except Blue, that's a color or a dog's name), but as a sibling set it's awkward. Lilah and Lachlan contain too many ls and therefore it becomes a tongue twister. You could use Delilah instead of Lilah and it would make things easier, though it still is a bit awkward. Maybe Catherine Lilah Marie and Lachlan Alexander Neel (Neel being a Hindu name for Blue)? You'd still get the names you like (minus Blue, but you get the meaning for that one), but Catherine and Lachlan work much better together than Lilah and Lachlan.