When you filter your contacts by those who are not subscribed to marketing emails, you may notice that the toggles for some contacts in the "Subscribed" column are a darker gray color than others.
Darker gray toggles indicate that you or another user on your account have designated the contact as "Not Subscribed" so that they will not receive marketing messages. These contacts can be re-subscribed by clicking the toggle to turn it purple.
Lighter gray toggles indicate that the contact "Unsubscribed" themself from your marketing messages. These contacts cannot be re-subscribed.