More diverse societies can help to reduce bias, prejudices, and stereotypes towards others to build inclusive and supportive societies. When a lot of groups live next to each other and interact without division on groups and classes, people learn that their pre-formed opinions are wrong through constant exposure to other groups and cultures. They learn to see people in a totally different light, which helps to overcome a barrier in assessing someone for the first time.
Whereas colorblindness could create a new, homogenous culture, where each of the groups adopts some of the solutions of another and eventually mix into a uniform society, it is not the case for multiculturalism. The latter implies that every culture is cherished for its uniqueness, however, it is not isolated because of it. We can learn from each other and still create fusions, simultaneously preserving our inherent traditions.