Sis and Billy Matching Color Fashions

Katy has a redheaded, bespectacled younger sister. 
In the original Woggon 1950s series, Katy's sister was a 
mischievous child around seven years old and known 
only as "Sis, the Candy Kid".

Katy's sister is infatuated wit Billy, and he with her; 
so they dress in matching fashions.