You can now simply use the accent-color property :
#cb1 {
accent-color: #9b59b6;
}
#cb2 {
accent-color: #34495e;
}
#cb3 {
accent-color: #e74c3c;
}
<input id="cb1" type="checkbox" checked />
<input id="cb2" type="checkbox" checked />
<input id="cb3" type="checkbox" checked />
Note : as this is a new feature, it is not supported by all browsers, but it is still useful
Here is a compatibility link