What point was David Hume making regarding his discussion of the missing shade of blue?

David Hume used the example of the missing shade of blue to illustrate his argument that our perceptions are limited by our previous experiences. He posited that because we have never experienced that specific shade of blue, we are unable to imagine it compared to the shades we have seen. This argument challenges the idea of innate ideas and emphasizes the role of sensory experience in shaping our understanding of the world.