The outline-color CSS property sets the color of the outline of an element. However, in many cases the shorthand property outline is more convenient to use and preferable.
An outline is a line that is drawn around elements (outside the borders) to make the element "stand out".
The outline-color property specifies the color of an outline.
NoteAlways declare the outline-style property before the outline-color property. An element must have an outline before you change the color of it.
outline-color: invert|color|initial|inherit;