Use the rule that scattering is proportional to 1/λ⁴…

Step 1. Blue against red. $\left(\dfrac{680\ \text{nm}}{450\ \text{nm}}\right)^4 = 1.511^4 = 5.21$.

Step 2. Violet against red. $\left(\dfrac{680\ \text{nm}}{410\ \text{nm}}\right)^4 = 1.659^4 = 7.57$.

Step 3. Violet against blue. $\left(\dfrac{450\ \text{nm}}{410\ \text{nm}}\right)^4 = 1.098^4 = 1.45$.

What do we see? Violet is scattered most, but the sky looks blue: the Sun sends less violet, and our eyes are less sensitive to it.