I disagree that preferences destroy a perfect world. Who even decided that a perfect world equals no preferences/choices. The fact that one can't have a preference/choice already defeats the idea of a perfect world [no freedom of choice in a perfect world sounds funny]. We are unique individuals, so it it is expected that we will have different opinions and preferences. But in a perfect world, these differences aren't going to cause anything bad. People are going to accept each other's choices, and won't discriminate. If you've watched the Barbie movie, it is similar to how the Barbies interacted with each other in the first part [ignore how they treated Ken and the old barbie].

If we have a choice between the color red and blue and both are perfect, how can we choose?

This is too funny. I feel like you are limiting your view of a perfect world. Do the people in your imagination of this only choose on perfection? And if the choices are both perfect, they get choice paralysis? To answer your question, we can choose similar to how we do it now. Maybe I used red yesterday, so maybe I'll choose blue today. Or my partner is wearing red and I want to match with her. Just because I like blue doesn't mean I'll use it everyday.

On a tangent, I have read that there are studies and theories that people might not be seeing the same color as everyone. The color we call blue might not be the same color from our perspectives. What I see as blue from my perspective, can be my red if I look from your perspective. Since there is currently no way to see what the other is seeing it hasn't been confirmed or denied as true. Using this idea in the perfect world scenario and adding some magic, our experiences can also be altered on the fly. If one likes a very sweet cake, and the other just likes a slightly sweet one, when they taste the same cake, it will be the perfect sweetness according to what they like.