Oops, it doesn't look like 'blue day' is a national day..

Other days

girl friend

Girl Friend Day
cat girl

Cat Girl Day
slime

Slime Day
get funky

Get Funky Day
pick me

Pick Me Day
mean girls

Mean Girls Day
boba

Boba Day
aloxolt

Aloxolt Day
bubble bath

Bubble Bath Day
book

Book Day