He said that, once he heard of the Christchurch attack, he had to do something.
"I thought, what would it feel like as a Muslim going to prayers today? I would feel a mixture of enmity and even fear."
"I picked up a card, wrote my message, went down to my local mosque at Barlow Rd and stood outside."
Every worshipper that arrived at the mosque was greeted by Graystone with a "salaam".
He said some of them were suspicious at first, thinking he was a protester, but warmed to him as they read the handwritten sign.
Inside the mosque, the imam commended him during the service.
"When people came out, I was surrounded by hundreds of people. People were thanking me, blessing me. Some people said their faith in humanity was restored."
Graystone says he belongs to a church but this issue transcends religion.
"It isn't really about religion. It's about community," he said.
"It's about friendship and community, and you have to take the first step sometimes and build bridges. At times like this, you have to choose between fear and friendship. You have to make that choice."