Not sure if anyone else uses Toyota Reference, but noticed something interesting that popped up on their site:
http://importarchive.com/scion/frs/paint
If you look at paint section, for 2018, no more hot lava and replaced by a yellow called "thunder". The paint codes (NAD) matches with the 2017 series yellow BRZ.
Mistake or accidental leak a few weeks before 2018 details go out? Argue among yourselves!