Let say you have a mixin for shadow like such:
@mixin box-shadow($offset, $blur, $color)
{
-moz-box-shadow: $offset $offset $blur $color;
-webkit-box-shado
You can't overload, but the typical practice would be to set defaults.
/* this would take color as an arg, or fall back to #999 on a 2 arg call */
@mixin box-shadow($offset, $blur, $color: #999) {
-webkit-box-shadow: $offset $offset $blur $color;
-moz-box-shadow: $offset $offset $blur $color;
box-shadow: $offset $offset $blur $color;
}