A gallery of shimapan sporting idols; as you may know, shimapan, an abbreviation of shima-pantsu (striped panties), are one of the new wave moe fashions to sweep the otaku landscape.
The archetypal example is light green horizontally striped pantsu, visible in a number of shots here, but generally the term also covers even vertically striped pantsu, and even diagonal stripes for the unorthodox. These however enjoy lesser status, or in some cases are shunned entirely.
The uptake of the fashion amongst actual females does not appear to have kept pace with the manciacal demand; such pantsu are not that widely sold, and for some reason ladies remain attracted to more conventionally fasionable or erotic underwear.
The major (virtual) idol depicted wearing these of late seems to be Hatsune Miku…