Very much like the Rio Grande is on the border of Texas and Mexico, a man who is described as being Rio Grande is on the border of being gay. Used for metrosexual or just questionable guys, usually ones into musicals or that are very stylish.
Guy to Friend:"I made a killing at the J.Crew summer sale and then watched 'Rent' for like like billionth time yesterday, it was awesome."
Friend:"Dude, you are so Rio Grande."
One of several rivers where the gringoes dump their shit into before reaching Mexico. All rivers that are shared by the Yanks and Mexicans flow from the EUA south into Mexico. In the case of the Colorado River, the Californians, Nevadans, and Arizonans pretty much take everything of value out of it before it flows south of the border.