I had to use Firefox to look at this (I totally forgot that that was a thing; I use Chrome Canary now and don't see it lol), but! I figured it out.

For your blue bubbles, you've got:

background-color: rgba(117, 195, 238, 1)

That 1 sets the opacity. In my code, I've set it to .4 which is why it's more transparent, so if you tweak that last number then that should do it!