When this picture was taken in December, 2013, winter was approaching in the southern hemisphere of Saturn, and with that even colder season came a blue hue to some of the planet’s clouds. The color is likely caused by a reduction of ultraviolet sunlight and the haze it produces. With less haze the atmosphere is clearer, increasing Rayleigh scattering (scattering by molecules and smaller particles) and methane absorption. Both processes make the atmosphere appear blue. A similar process cause the blue color of the clouds on Uranus and Neptune.
BTW, it’s now spring in the southern hemisphere of Saturn.
Image Credit: NASA