Indeed, will note this one as well 🙂
In the meantime you can style it like so:
[html].probox .proclose svg {
background: #333333 !important; /* the bg color */
fill: #ffffff !important; /* the cross X color */
box-shadow: 0px 0px 0px 2px rgba(255,255,255,0.9) !important; /* the border width and color */
}[/html]