"Father Conmee sat in a corner of the tramcar, a blue ticket tucked with care in the eye of one plump kid glove, while four shillings, a sixpence and five pennies chuted from his other plump glovepalm into his purse." (U10.115)
The color of a ticket reflects its price, hence the distance one could travel with it. Father Conmee bought a blue ticket. Before 1918, blue was a penny ticket.