Time for my final prediction on the featured members of this event.

So, the orange has to be Nanami, that's a given.

The blue, I think is Hina. The color of the blue bubbles in the banner most closely match Hina's color. Here's a comparison:

From left to right, The bubble's color, Hina's color

The pink could be Aya. Again, the colors most closely match. Although, it could also be Rimi. Here's a comparison:

From left to right, the bubble's color, Rimi's color, Aya's color.

The yellow is probably Tsugumi. Here's a comparison of the colors:

From left to right, the bubble's color, Tsugu's color.

Not sure where the other color is on the banner. It could be the other yellow, so maybe Kokoro, but probably not.

Edit: Oh, maybe Saaya is the other yellow. She hasn't had an event 3* since January and hasn't had a gacha 3* since June.

Note: I got all these colors from the BanG Dream! Wiki.

Edit again: Okay, more predictions. I think Tsugumi will be the event 3* and Saaya will be the gacha 3*. And I'm sorta thinking now that Aya won't be a featured member, since Rimi hasn't have an event 2* since July.

MORE PREDICTIONS! I've changed my mind about Rimi being the 2*. I think it'll be Saaya because she hasn't had an event 2* in over a year. Rimi will probably be the gacha 3*.

Edit AGAIN: Here's the problem with the other yellow. There's two other yellows. One (the star) more closely matches Kokoro:

But the one at the bottom of the title more matches Saaya:

So I'm really confused.

I may even be completely wrong. These yellows might not even mean anything, but we'll see.