CSS Property:
text-decoration-color:

Note: The text-decoration-color property is not supported in any of the major browsers.

Note: Firefox supports an alternative, the -moz-text-decoration-color property.

Result:
Hello world!
CSS Code:
#myDIV {
    text-decoration: underline;
    text-decoration-color: red;
}
Click the property values above to see the result
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