References:

• Moving to zsh, part 6 – Customizing the zsh Prompt
• 256 COLORS - CHEAT SHEET
• 256 Terminal colors and their 24bit equivalent (or similar)

# ------------------------------------------------------------------------------
# Customize PROMPT
# ------------------------------------------------------------------------------

autoload -Uz vcs_info
precmd_vcs_info() {
  vcs_info
}
precmd_functions+=(precmd_vcs_info)
setopt prompt_subst

export PROMPT="%F{196}%B%(?..?%? )%b%f%F{117}%2~%f%F{245} %#%f "
export RPROMPT="%B\$vcs_info_msg_0_%f%b"

zstyle ':vcs_info:git:*' formats '%F{240}%b %f %F{237}%r%f'
zstyle ':vcs_info:*' enable git

In iTerm2 make sure to enable Use built-in Powerline glyphs.

How this looks: