Blue Lagoon is a pretty light blue color with a little shimmer to it, the only problem with it is that it's a little sheer, but kind of gloopy, so when I try to apply it it slides down to my cuticle and the middle of my nail still needs another coat. But besides that it's very pretty.
Portia, on the other hand, is small iridescent glitter suspended in a super sheer light blue jelly base. It's one of the prettiest colors I've ever seen.
In this picture I've layered Portia over Blue Lagoon, and although it's hard to see the true prettiness on my fingers, but you can definitely see it better in the bottle. All in all, I would say Portia is a must buy, and super pretty, but you could find a way better light blue the Blue Lagoon.