MDN URL: https://developer.mozilla.org/en-US/docs/Web/CSS/border-color

What information was incorrect, unhelpful, or incomplete?

/* horizontal | vertical */
border-color: red #f015ca;

/* top | vertical | bottom */
border-color: red rgb(240,30,50,.7) green;

Here "horizontal" would need to equate to "top & bottom" to match browser behaviour which is the opposite of what horizontal means. And same for "vertical"

Specific section or headline?

Syntax

What did you expect to see?

• to match the border-style syntax and avoid confusion this should be written as:

/* top and bottom | left and right */
border-color: red #f015ca;

/* top | left and right | bottom */
border-color: red rgb(240,30,50,.7) green;

Did you test this? If so, how?

https://codepen.io/davidelrizzo/pen/gOLzgdG