Yes, the focal length of a lens depends on the colour of light.According to lens-maker's formula,f1​=(μ−1)(R1​1​−R2​1​)Here, f is the focal length, μ is the refractive index, R is the radius of curvature of lens.The refractive index (μ) depends on the inverse of square of wavelength.The focal length of a mirror is independent of the colour of light.