Hey, @goobernacular moved this to the support forums to clear up the announcement thread from support.
The badge color now inherits "paletteAccent3", you can change that to:
rgb(224, 48, 48)
Which is the old color. That color palette is really only used for badges/other alerts so it made sense to match that color.
The sub-nav should inherit the background color from the selected tab, we don't make a change there from the default XF setup. You can choose your own color: Style properties -> Header and navigation -> Sub-navigation row.