The Series.Yellow starts with the mildly updated 2017 BRZ and stacks the new Performance Package (Brembo brakes, Sachs dampers, black 17-inch wheels) on top of the Limited trim. The Series.Yellow will come with the six-speed manual only, as it's required to get the Performance Pack. That also means it has the new 205-hp boxer four and a different final-drive ratio to go along with it.
Aside from the yellow paint, exterior differences include black Subaru and BRZ badging, and a black surface for the rear spoiler. The interior gets it some yellow as well, with stitching on the seats, door panels, dash, steering wheel, floor mats, and shifter and e-brake boots. The interior grab handles are yellow-ized, and there are yellow patches at the top of the seat bolsters. Oh, and the seats have Alcantara inserts, but those aren't yellow.
As the second in the Series series, it follows in the footsteps of the BRZ Series.HyperBlue from 2016. There's also precedent for special yellow Subarus, as 1,000 XV Crosstrek Special Editions from 2015 got yellow paint and black cladding. Yellow!