My suggestions:
1) Agree with the other response, you need to buy a bigger black dildo ASAP. In a way you have been depriving her of one of the main turn ons of this lifestyle. A BBC. The stereotype isn’t true 100% of the time obviously but true often enough that women everywhere, unless they were living under a rock, associate black men with bigger cocks. A bigger cock will go deeper, give her a more filling experience, will hit places you can’t, will stretch out her pussy, curl her toes, blow her mind and give the most intense orgasms of her life.
2) Do NOT show her professional cuck/interracial porn. it’s weird, awkward, often unbelievable, and the fake orgasms aren’t hard to spot. Show her amateur interracial porn with real wives and girlfriends being pleasured by well hung black men.
Two of my favorites
Hot wife's bbc creampie
www.blacktowhite.net
xhamster.com
Don’t get hung up on hair color. Her seeing real white wives or GFs losing their mind in ecstacy will get her far wetter and turned on than just seeing someone with the same hair color as her. Besides, most likely she will be watching the guys fucking the ******* out of them not looking at their hair.
3) Tell her the truth that your number one fantasy above all others is to watch her get massively pleasured by a well hung black guy. This fantasy is not a way to get her to be ok with you sleeping with other women. It’s about watching her pleasured (compersion), (sperm) competition is a part of it for me, maybe the taboo, color contrast etc. But also tell her (only if it’s true which it sounds like it is) your biggest, maybe only reluctance to doing this in real life is that you love her so much, and love the relationship you have built together, and it would be devastating and not at all worth it to risk losing her to someone else. That puts things in perspective that as hot as this is for you, she is more important to you.
4) was true for me, maybe it might be true for you. I told my very conservative wife years ago that it would really turn me on if I watched her dance with a black guy. She said, “oh I don’t think I could do that.” “What? Why not?” “I would be too embarrassed to go up and ask a black guy to dance.” When I clarified that I was talking about if a black guy asked her to dance, she said, “Oh, that’s totally different. Sure if a black guy asked me to dance no problem.” She did one time and it was so fucking hot. He was practically drooling as he eye fucked her. We had great sex later talking about it.