I did two different dilutions of $\ce{FeCl3}$ (within a $\pu{1h}$ timespan) from $\pu{0.05 M}$, and the one with $\pu{5E-4 M}$ concentration looked a darker orange than the one with $\pu{5E-3 M}$.
The picture shows on the left: $\pu{5E-3 M}$ (I erased the label on the flask); on the right: $\pu{5E-4 M}$
I did a test with litmus paper, which showed that the more concentrated one ($\pu{E-3}$) was more acidic, which makes sense. I also did a rates test ($\ce{FeCl3 + H2O2}$), and the more concentrated one made the reaction happen faster, which again makes sense. Why, then, does the more concentrated $\ce{FeCl3}$ look lighter coloured?
Since I had made the more dilute one ($\pu{E-4}$) before, I thought there might have been more time for the ferric hydroxide to precipitate and form a darker colour. But I had only left it for $\pu{1h}$. I also thought that since the more concentrated one looked greenish, $\ce{FeCl2}$ might have been made, yet this does not seem plausible as $\ce{FeCl3}$ is more stable.
