Should casting be color-blind?

I’m just wondering if you think casting should be colorblind (i.e. casting without taking the race of the actor into account) or not? Are there times when it is and isn’t appropriate? What are those for you? For example, I would have a hard time watching a film with Meryl Streep cast as Harriet Tubman. Streep is very talented, but I don’t think any white actress could pull off Tubman in a believable way, but maybe you disagree.