The phrase "red pinstripe" refers to a thin line or stripe that is of the color red. It is commonly used to describe clothing, especially suits, which have very narrow red stripes running parallel to each other. Full definition
You can even choose grey socks with red pinstripes for style. (myntra.com)
Customers likely want to show off that they have a limited edition WRX, so STI adds Cherry Red pinstripes around the mesh grille and rear bumper. (motor1.com)
Jean Paul Gaultier Homme unisex vest of lightweight wool blend in charcoal grey with broken red pinstripe throughout... This vest closes at the front with buttons, has button straps at t... (1stdibs.com)