This is the 540th most frequent Norwegian word.
blå
Blue.
'Blåtur' is a compound noun where 'blå' figuratively implicates mystery or spontaneity.
Hun gikk på blåtur med vennegjengen.
She went on a spontaneous trip with her group of friends.
In this context, 'blå' describes the color of the sky, used as an adjective.
Himlen er blå.
The sky is blue.
Here, 'blått' is the neuter singular form of 'blå', agreeing with the noun 'kort' (card), serving as an adjective with agreement.