The ‘outline-color’ property specifies a color for the outline for an element.
The outline properties create a uniform line around an object in order to draw visual attention. An outline is slightly different than a border in several ways: An outline is drawn starting “just outside the border edge” and is allowed to be non-rectangular. Outlines are always rendered on TOP of an element’s rendering box and do not influence the box’s position or size calculation; the document does not need to be re-flowed when a border is rendered or hidden, but the outline may overlap other nearby elements.
<img src="image.gif" style="outline-color: green">
inherit: Explicitly sets the value of this property to that of the parent
invert: This value inverts the color of the outline to the opposite value of the color “underneath” the outline to ensure proper contrast
color: Sets the border to the indicated color value