-moz-border-right-colors

The CSS -moz-border-right-colors Mozilla extension property sets a list of colors for the right border. When an element has a border that is larger than a single CSS pixel, each line of pixels uses the next color specified in this property, from the outside in. This eliminates the need for nested boxes. If the border is wider than the number of specified colors, the remaining part of the border is the innermost color specified. It does not apply if  is   or , as well as to tables with. To specify the colors of the other sides, use the,  , and/or   properties.

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Image example: