So

A little history me and my wife and I late 30s have 2 kids. I recently bought some dildos as a joke but after watching her with one it's now all I think about. I've told her how much it turns me on watching her fuck another cock and it clearly turns her on when I watch her. Whilst sexting she has said he would like to be watched whilst fucking me to show everyone how much of a slut she is. But when I mention her having another man she says she only wants me to fuck her. Now I really want to make her come around to the idea on her own of cuckolding with a bbc but she has said she doesn't like the "look" of black cock.

How is best to start this happening and open her up to the world.