Those who love to wear plaid shirts, hipsters.

A vagina concealed in plaid underwear.

Totally ghey. In the mid 1970's they were once thought of as cool. Now, abercrombie drones have sodomized the name and ruined yet another thing that was once cool.
By the way guys... You may find them cool, but your grandfather also has a pair. So...

Madras Plaid is a type of fabric that originated in the Southern city of Madras, India, now known as Chennai, and was woven on looms by hand or machines, and the fabric itself is a pattern of various lines of different colors, intercrossing at pre-designed distances, making a check pattern, but with larger, and not necessarily geometrically symmetrical lines.
Madras Plaid was made hugely popular, when initially its colors were not fast, and would bleed (bleeding madras), and hence, after a few washes, the resultant fabric would have a worn out, vintage look, making it very desirable to some fashion aficionados, especially the Ivy league set, the preppy fashionistas and among vintage menswear lovers.
Hence, Madras stuck around, and even though, today's Madras is not bleeding, it still is a very desirable clothing item.
Today, the largest collection of Madras Plaid fabric is available online at various fabric stores like fabriconlinestore.com and others, and can be ordered by the yard or wholesale.

Wearing plaid, as the stereotype goes, is a lesbian identifier . Typically , it is worn by masc/butch lesbians as a plaid shirt .

So far as colours go, sparkly plaid is just about as good as they get. Popular belief states plaid to be a pattern, sparkly naught but an embellishment. This common misconception is crap.

The demographic of private- or parochial-schooled people, usually white females, who act in an excessively flamboyant manner, usually with some degree of sexual promiscuity. Derived from the typical color/pattern of schoolgirl uniforms.