I just purchased a white Box style & it seems to be the perfect size & color for all occasions. I really wanted a summer bag so that is why I chose white. I like the fact that a white bag is kinda like a black bag in the sense you can pretty much wear it with any other color. Although, you do have to be really careful with white. Good luck.
I'd say pink too as they've released so many gorgeous blues already but not that many pale pinks. Although if you included ink in your choices I would definitely pick ink!!
I have all three colors and they're all fabulous! However, the white and pale rose IMO are summer colors. The cornflower blue IMO can be used in all four seasons, so maybe for your first Balenciaga it would be the best choice. Btw, my cornflower City was my first Bbag.