The new default looks like this (like in docs/userguide):
colors {
background #000000
statusline #ffffff
focused_workspace #ffffff #285577
active_workspace #888888#222222
inactive_workspace #888888#222222
urgent_workspace #ffffff #900000
}
If you want to go back to the previous colors, use:
colors {
background #000000
statusline #ffffff
focused_workspace #ffffff #480000
active_workspace #ffffff #480000
inactive_workspace #ffffff #240000
urgent_workspace #ffffff #002400
}