Hahas. :D Yea, I know that. Anyway, is it compulsary to wear blue
or optional?
Is not compulsary if you are wearing blue colour t-shirt,
can wear other colour t-shirt if you are going to other station.

Discover the
Circle Line Stars Contest
Come dressed in the event theme "CONNECTIVITY"
& be discovered as one of our Circle Line Stars! For example,
wear t-shirts with a train theme or come in the colors of the
station that you are starting the tour from (see below). Be the
most creative & stand a chance to win attractive prizes! 5
lucky stars will be spotted every session.
*You are encouraged to dress in the colours of your
respective reporting stations.
Bartley = Red
Serangoon = Green
Bishan = Blue
Lorang Chuan = Orange
Marymount = Yellow
(Prizes: Limited-edition LTA
gifts).