When looking at the colors: primary are blue, red, yellow and secondary are green, purple, orange. Traditionally, orange is blue's complementary color that is often used in art/design color theory. Ginger+green plays on green being red's complementary color (even though gingers appear more orange than red).
Below is a color wheel. The art above has ginger more the middle between orange and red (though leaning orange) - you'll notice that the green used in her suit is nearly the exact complement green-blue. For Austin, the swimsuit is close in hue to the ginger hair, but leans even just a smidge more orange to complement the lighter blue of Austin's hair.
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