[css] Is there a 'box-shadow-color' property?

No:

http://www.w3.org/TR/css3-background/#the-box-shadow

You can verify this in Chrome and Firefox by checking the list of computed styles. Other properties that have shorthand methods (like border-radius) have their variations defined in the spec.

As with most missing "long-hand" CSS properties, CSS variables can solve this problem:

#el {
    --box-shadow-color: palegoldenrod;
    box-shadow: 1px 2px 3px var(--box-shadow-color);
}

#el:hover {
    --box-shadow-color: goldenrod;
}