Five inks, and when to reach for each
A highlighter is a reading tool, not a decoration. Five pigments, and which one you reach for is a claim about why the sentence matters: a definition, a warning and a number all want different colours.
A pen box has five colours in it and a student uses all five, but not at random. Over a term a private grammar develops: one colour for the thing that will be examined, another for the thing that was surprising, a third for the thing to come back to. Nobody writes the grammar down and everybody has one.
The same grammar is worth having on a page you publish, because a highlight makes a claim and the reader can tell when the claim is inconsistent.
The five, and what they are good at
Yellow is the default, and the only one that disappears. It is the lowest-contrast of the five against a light page, which is exactly why it is right for the sentence you would underline in a book you own — present when looked for, invisible when reading straight through.
Green marks the thing that turned out to be true. A conclusion, a measured result, the sentence that survived being checked. It reads as settled, which is why it is wrong for anything provisional.
Pink is for the correction. The place where the obvious answer is the wrong one. It is the loudest of the five on a light background and the one to spend most carefully.
Blue is the aside — the definition, the piece of context, the thing you would put in a footnote if the footnote would actually be read. It is cool enough to sit under body text without pulling the eye off the line.
Orange is the warning that is not yet a warning. The trap, the thing that will cost an afternoon. It sits between yellow's quiet and pink's alarm.
The rule that makes it work
One colour per meaning, across the whole site, forever. A highlighter used for emphasis alone is just bold with extra steps; a highlighter used consistently is an index the reader builds without being told they are building one.
And use fewer than you think. A page with nine highlights has none, because the eye stops treating a colour as a signal once it is the most common thing on the page.
The grammar, written down once
The point of writing it down is not obedience, it is arbitration: six months in, when a sentence seems to want two colours, the table answers instead of a coin toss.
| Ink | Claims | Never for |
|---|---|---|
| Yellow | worth re-finding | anything urgent |
| Green | checked, held up | a hope, a plan |
| Pink | the intuitive answer is wrong | mere emphasis |
| Blue | context, definition | conclusions |
| Orange | will bite later | things that already bit |
The last column earns its place. A grammar is defined at least as much by what a colour must never mark as by what it may, the same way a style guide's banned words do more work than its recommended ones.
The pencil and the ballpoint
The highlighter is not the only thing on the desk. Two more gestures, straight from any borrowed textbook: the sentence worth underlining gets a pencil line under it, and the single word everything turns on gets ringed in ballpoint.
An underline claims less than a highlight — it says "noted", not "this will be examined" — and it stacks: a sentence can be highlighted for the term and underlined on the second pass, exactly as paper accumulates readings. The line takes a colour when it needs one: a conclusion can be underlined in green, a warning in orange.
The ring is for a word, not a sentence. The word that must cease, the number that is wrong, the term about to be defined — một chữ thôi. Ring a whole clause and the loop stops meaning anything.
Why it is drawn and not filled
A coloured rectangle behind text is not what a pen does. A real stroke has chisel ends where the nib entered and left, it does not cover the descenders evenly, and it breaks at the end of a line rather than wrapping as one continuous block. Drawing it as an SVG stroke costs a reader 1.4 KB and nothing at all on a page with no highlight on it.