Colgate-Palmolive Co. will try to take a bite out of rival Procter & Gamble’s lead in the fast-growing at-home teeth-whitening market with its own entry-a gel that costs less than half the price ($14.99) of competing Crest’s Whitestrips. The system comes out more than a year after P&G introduced Crest Whitestrips in stores.The New York-based company today launches Colgate Simply White, a gel that whitens teeth in two weeks-the same amount of time as Whitestrips-using a toot...