yellow and pink is fun ^-^ I just finished a commission using those as the primary colors actually.

I think the reason they are so fun together is that yellow and purple are complementary colors on the color wheel and pink is close too purple, yet in general i think pink is more of a fun color ^_-
in color theory pink would more match dark green, but seeing as pink in art is often not just red and is a mix of light purple and light red. then the compliment would be dark yellowish green... i think... heh XP