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(WJW) — The beloved Shamrock Shake will return to McDonald’s restaurants later this month.

The chain tweeted Wednesday that the shake will be available at participating restaurants starting Feb. 21. The limited-edition shake is only available for a limited time every year to celebrate the St. Patrick’s Day season.

The Shamrock Shake is vanilla soft serve ice cream with a minty flavor and finished with a whipped topping.

McDonald’s will also offer the fan-favorite Oreo Shamrock McFlurry starting Feb. 21, according to a press release from the company. The McFlurry is also vanilla soft serve with mint flavor, plus Oreo cookie pieces.

As an added bonus, the chain is sharing the “secret ingredient” that makes the green color so iconic: the hex code for the Shamrock Shake color: #cbf2ac. A hex code is a way to identify a very specific shade of a color in HTML and other code.

That code could win customers something starting later this month, the fast-food chain hinted.

“Starting Feb. 21, our Shamrock green hex code just might unlock another tasty secret. That is, if you know where to look. Be one of the first to figure out the mystery and you could get a little something special from us,” said the release.