Often the bride will wear an heirloom, or maybe carry a family bible or prayer book, the dress of course is usually the something new, and they will borrow something from someone to wear. The something blue can be difficult, but a lot of brides get round this by wearing a blue garter under their dress.
Within the "white wedding" tradition, a white dress and veil would not have been considered appropriate in the second or third wedding of a widow or divorcee. Nowadays it really isn't an issue.
Before the white wedding dress became "traditional" an old poem (which seems to favour blue) sang the praises or woes of various colour choices.