zsh-syntax-highlighting / highlighters / main

This is the main highlighter, that highlights:

Commands
Options
Arguments
Paths
Strings

How to activate it

To activate it, add it to ZSH_HIGHLIGHT_HIGHLIGHTERS:

ZSH_HIGHLIGHT_HIGHLIGHTERS=( [...] main)

This highlighter is active by default.

How to tweak it

This highlighter defines the following styles:

unknown-token - unknown tokens / errors
reserved-word - shell reserved words
alias - aliases
builtin - shell builtin commands
function - functions
command - commands
precommand - precommands (i.e. exec, builtin, ...)
commandseparator - command separation tokens
hashed-command - hashed commands
path - paths
globbing - globbing expressions
history-expansion - history expansion expressions
single-hyphen-option - single hyphen options
double-hyphen-option - double hyphen options
back-quoted-argument - backquoted expressions
single-quoted-argument - single quoted arguments
double-quoted-argument - double quoted arguments
dollar-double-quoted-argument - dollar double quoted arguments
back-double-quoted-argument - back double quoted arguments
assign - variable assignments
default - parts of the buffer that do not match anything

To override one of those styles, change its entry in ZSH_HIGHLIGHT_STYLES, for example in ~/.zshrc:

# To differentiate aliases from other command types
ZSH_HIGHLIGHT_STYLES[alias]='fg=magenta,bold'

# To have paths colored instead of underlined
ZSH_HIGHLIGHT_STYLES[path]='fg=cyan'

# To disable highlighting of globbing expressions
ZSH_HIGHLIGHT_STYLES[globbing]='none'

The syntax for declaring styles is documented here.