The last time I saw a red-fleshed apple, such as a Rome, was on the East coast. I presently live in CA so I rarely encounter them now. I have to agree with the first reply to this question as deep red apples can leach the skin color into the flesh but there’s no risk or issue with red. read more
It's caused by sunlight on the skin which turns it red & some years more than others it seeps through; apple growers call it 'bleeding'. It's a natural phenomenon. All my Cox's on the sunny side of the tree are like that this year. read more