I think the flaw in your reasoning is the assumption that chemical reaction is causing the sensation of blue.

But imagine if the consciousness and what it senses cannot be separated. So the consciousness sensing blue and the chemical reaction happening in the brain, are just correlated. One did not cause the other.

One can ask where that correlation came from. I think that the such correlations are inherent in such worlds where consciousness is possible.

I think everything that we observe as physical laws, causality etc, are just such correlations.