This is somewhat fitting. A bit of analyzation involved.



Fluttershy and Pinkie Pie fits their seasons in personality, and to some extent, colour. Fluttershy has the caring and nurturing nature of spring and she usually wears green, a colour commonly associated with that season. And not to mention some flowers, which frequently bloom in the spring, are coloured blue/cyan, pink, and yellow (there is even one blue flower in the picture). Colours which Fluttershy also has. The sun also shines a bit yellow in the picture.



Pinkie has the fun and spicy element of summer. Summer could also be interpreted as fiery, although Pinkie doesn't really have that trait. The water in the picture gives off a bright blue colour, which corresponds to the blue in Pinkie's eyes and cutie mark (although she's wearing shades, though). I also love how you have her sunglasses with a yellow frame, a yellow ducky tube, and a lemonade. Which further gives appeal to Pinkie's image, for the yellow in those items correspond to the yellow (although a small amount) in her cutie mark.



While Rarity and Applejack fits their seasons in terms of their colours. Although I could be a bit wrong here. The dominant white in Rarity corresponds to the white snow, which is also quite dominant in the winter. The blue, purple, violet, or indigo in Rarity's other parts are accents which match the rather melancholic skies of a winter night with the Moon shining.



Applejack in general looks just as orange as the fall. Red and yellow looks fitting on both the season and the pony. Her hat also corresponds to the colour of the soil and the trunks of the trees. Fall or autumn is the season of harvest, and we see Applejack harvesting or at least carrying a variety of apples in the image. Apples come in different colours such as red, gold, and green.