Your eyes and the turn signal in your car are blinkers. The Blinker probably has nothing to do with either of them, as the cocktail's origins are unknown. Patrick Gavin Duffy, a New York City bartender in the late 19th century and pre-Prohibition 20th century, mentioned the Blinker in his 1934 book The Official Mixer's Manual. 75 years later Ted "Dr. Cocktail" Haigh resurrected it. Here's my version.

2 ounces rye
.75 ounces grapefruit juice (1/8 grapefruit)
.5 ounces glorious grenadine or raspberry syrup

Combine in a shaker with ice, be like the Cars and Shake It Up (1980s music fans like me get it), and strain into a chilled glass.  Grapefruit or lemon peel garnish optional.

Duffy's Blinker used a 3:2:1 ratio of grapefruit juice, rye, and grenadine. I adapted it with a vague Whiskey Sour formula. Besides the ratios of ingredients, the sweetener is the real variable. The original uses grenadine, and Haigh uses raspberry syrup. I prefer the Blinker with grenadine. If you want to make your own raspberry syrup, make a batch of super simple syrup. Mash raspberries into the mixture when you remove it from the heat source, then after it cools down strain out the solids. 

The Blinker is a little spicy, refreshing, and quite drinkable. If you have too many you'll channel some Blink-182 tunes, forget All The Small Things, and ask What's My Age Again.  Or channel the Cars tune and let the Good Times Roll.  Blink-182 makes good music, but I grew up with the Cars. Regardless of your taste in rock n'roll, you'll enjoy the Blinker for much longer than a _____ of an eye.