Most twins find that teachers get them muddled up at school. But four-year-olds Marcia and Millie Biggs, who are starting reception class at Osborne Infant School in Birmingham today, won't have that problem - because they have different skin colours.
Marcia has a fair complexion, with blonde hair, like her mother, while Millie takes after her dad, who is of Jamaican origin.
In fact, their mum Amanda says that the main struggle is getting people to believe they have the same parents.
'People still just can't believe they're related, let alone sisters... Even teachers at nursery refused to believe they were sisters,' she said. 'But I've become used to it after four years.'
Amanda and her husband Michael had been together for 10 years when they conceived the girls through IVF treatment.
Experts say that the chances of two twins being born different colours are around a million to one.
Dad Michael said: 'When people see them they often do double takes because they can't believe what they're seeing.
Today will be a big day for the family, but Michael said girls were looking forward to school, he said. 'They have different personalities and Marcia liked to think she was in charge while they were at nursery, but Millie was the bossy one at home.
'Hopefully they will feed off each other and enjoy themselves!'