Le Mans Blue vs Interlagos Blue
Le Mans Blue and Interlagos Blue shown here on the E92 M3, these were the only two blue paints available from the standard range on the E9X M3.
While both may be hard to distinguish from one another when seen individually the differences are pretty clear when putting them next to each other as seen here, even in the overcast conditions of these images. Le Mans Blue, seen on the left, is clearly a lighter shade of blue compared to the darker Interlagos Blue on the right. Interlagos has more of a subtle purple undertone while Le Mans is a more pure blue.
Both great colors that are only available as an Individual paint option nowadays.