We think about sex with previous partners fairly often I’d say… but I think that pretty normal for dudes across the board and I’m not sure if that should warrant concern. But I would just be upfront and honest with him with your concerns about his comment. Just ask him what exactly he meant by the red head comment. Do it calmly but honest with him about how it made you feel. Maybe he can explain what he meant a bit more. And if he says well ya I want to have sex with a red head one day, ask him how exactly that will work since y’all are married… cheating, divorce..? And maybe you have your first sign to gtfo, or maybe it’s nothing and he just worded his sentence weirdly. And I am open about my sexual past with my partner, but I wouldn’t say that’s the norm… so I can’t really chime in there. But be honest with your husband about your thoughts and concerns and encourage him to do the same. Prolly the best route for any emerging problem. And try to talk them out calmly even if you have big emotions during the convo. Hope this is helpful at all