A simple function to do the job is:
function deCase(s) {
return s.replace(/[A-Z]/g, function(a) {return '-' + a.toLowerCase()});
}
alert(deCase('scrollbarDarkShadowColor')); // scrollbar-dark-shadow-color
There are likely many other ways.
Also, you can do camelCase using:
function camelCase(s) {
return s.replace(/-(.)/g, function(a, $1){return $1.toUpperCase();});
}