change icon based on another object

[admin]

grp.listen will skip unknown group addresses. This does not produce any errors so it won't affect other groups.

AND logic can de defined via CSS but you need to assign a different class in each grp.listen callback.
For example this rule only applies to elements that have both off-a and off-b classes.

Code:

.off-a.off-b {
  background-color: red;
}