Visits appear greyed out on the visit screen when either the client record or carer record linked to the visit is inactive.
It's designed to be this way so you can isolate these visits and investigate them to see if an inactive client still has visits assigned to them, or if an inactive care worker has been scheduled to complete a visit.
To reconcile these visits, you need to identify if the visit is grey due to the client or the carer, and either remove the visit from the client or assign a new carer to the visit.