A truly color-blind society would include casting in movies and television with little to no regard for skin color or ethnicity when such considerations have nothing to do with logical story points. Of course there are instances where a particular color is important to a story, for instance a story about a Mexican immigrant family would not work so well if the cast for the family was a mixture of different ethnicities and did not look Mexican. You wouldn’t want to pull the audience out of the story by causing them to wonder what is going on.
But there are many cases where skin color or ethnicity have nothing to do with anything. And in those instances it is great that sometimes Hollywood does open up the possibilities. One well-known example was the casting of Lou Gossett Jr. in “An Officer And A Gentleman.” Originally his role was envisioned as a White male. But since in the end the ethnicity or color of the Officer had nothing to do with the story, Gossett was able to get the role and audiences everywhere benefited.
Here is an article on some other notable movie roles where the ethnicity of the character was changed in casting from what was originally written.