The terminal escape sequence the GHOST SUGGESTION is drawn in — grey, so it reads as something offered rather than something typed.

Not a theme capture and not red(): this is one colour, for one piece of text, and the only question about it is how dim "dim" should be on the terminal you are actually using. Which is why it is read from the environment.

Read from the environment rather than guessed at, because "muted" against a light terminal and against a dark one are different colours and only the developer knows which they are on. QUNITX_SUGGEST_STYLE is the direct spelling; ZSH_AUTOSUGGEST_HIGHLIGHT_STYLE is honoured when it has been exported, since somebody running zsh has already answered this question once.

import { mutedSuggestionStyle } from './completion.ts';

mutedSuggestionStyle().startsWith(String.fromCharCode(27)); // true — an SGR sequence either way