There are quite a few great pictures of Portimau Blue in showrooms and on display at auto show booths. Here is a set of pictures and a video that give you a better visual representation of the color next to a few other BMW blues.
The online configurator shows a color that looks like it could be Estoril Blue. It's not. Portimau Blue is a slightly deeper and more vibrant blue. It appears to me that it may have a few flecks of San Marino Blue, but then again it was parked next to the CS
From left to right in the first picture:
San Marino Blue M3 CS Sedan
Portimau Blue 330i xDrive Sedan (G20)
Estoril Blue 440i Gran Coupe
Yas Marina Blue M3 Sedan with Competition Package
Enjoy!