Stocks Open Down, Oil Up, Colgate Warns  NEW YORK (Reuters) - U.S. stocks opened lower on Monday as  oil prices rose above \$46 a barrel, increasing concern about  corporate profits, while personal products maker  Colgate-Palmolive Co. &lt;A HREF="http://www.investor.reuters.com/FullQuote.aspx?ticker=CL.N target=/stocks/quickinfo/fullquote"&gt;CL.N&lt;/A&gt; warned about earnings.