When I go to text a new message on my iPhone, the persons name and phone number comes up gray?

Ok so I went to go start a new chat with a person on my iPhone, and their name and number came up grey? The other names and numbers are coming up either blue or green except for like 3 others that are coming up grey. What does this mean?

The manufacturers of the mobile device could have made it that way but you can double check the system details with the phone manufacturer if you like which in this case is apple

When the recipient is a known iMessage (Apple) client, the name will be green. When the number is from your known contacts (or previously used), it's blue. A name that is not already recognized by the phone will appear gray. After a successful text (iMessage or SMS), it'll appear blue next time.