Sins are not 'covered' by Jesus' blood and thus made invisible to God. In fact, Jesus' ministry can be summed up as one which taught and forgave sins. Forgiveness washes the sins away so that no stain remains. Jesus sacrifice did away with the requirement for an annual day of atonement and also for our individual requirement to publicly offer an animal sacrifice throughout the year whenever we had sinned. Instead, we are to offer ourselves in an unblemished state.
Forgiveness removes the stain.