This pattern is available in Norwegian and English.
The hat is worked at circular needle, bottom up, starting with rib.
Do the choice of colour like this: if the person you are knitting for is single, choose green with an S, if not, choose red whit an N, and should you somehow be in doubt, choose yellow with an O.
As a joke for 1th of April 2014, The Norwegian Trekking Association (DNT), announced a new sort of marks. DNT’s traditional marks are the red ones, to show the route where to go. Now they would recommend to use different colour at the hats, to show whether one where single or not. People loved the idea, and made the joke come real.
Aud B liked the idea to, and here it is.