app/assets/stylesheets/attendance.scss
$attendance-state-color-invited: $color-gray-dark;
$attendance-state-color-attending: $color-green-dark;
$attendance-state-color-declined: $color-red-dark;
img.circle.attendance-state-invited {
border-color: $attendance-state-color-invited;
}
img.circle.attendance-state-attending {
border-color: $attendance-state-color-attending;
}
img.circle.attendance-state-declined {
border-color: $attendance-state-color-declined;
}