While most colleges require two years of a foreign language, some (e.g. Stanford; see below) require three.
Some colleges accept four years of study of Latin in High School as fulfilling their language requirements (e.g., the College of William and Mary in Virginia; see here).
Colleges also tend to look favorably on students who have completed at least three years of a foreign language as it demonstrates dedication and commitment.
“Three to four years of a language shows follow through and a deeper level of interest.” Michael C. Behnke, Vice President for Enrollment, University of Chicago Source.
“[. . .] depth and mastery are important in the serious study of any discipline. The student who is willing to do more than the minimum is always more appealing.” Ray Brown, Dean of Admissions, Texas Christian University Source.
Harvard University: "we recommend ... Four years of a single foreign language" Source
University of Michigan: "Freshman applicants to the College of Literature, Science, and the Arts are strongly encouraged to take four years of language study, but only two years of the same language are required for admission." Source
Williams University: "While there are no absolute requirements for admission, competitive candidates typically study English, math, natural science, foreign language and social studies in four-year sequences and present a distinguished record throughout their secondary school career. Source
Source: Allen Grove, "Foreign Language Requirement for College Admissions"
Latin is often viewed at least as favorably as other languages, and in some cases moreso:
“Students taking Latin are typically scholarly." Matthew Potts, Admissions Counselor, University of Notre Dame
“Classical languages on a transcript indicate seriousness of purpose and true devotion to a rigorous program of study.” Fred Zuker, Vice President and Dean of Student Services, University of Dallas
“We consider students who study Latin seriously (with strong, steady performance) to be excellent candidates for Bryn Mawr.” Elizabeth Mosier, Acting Director of Admissions, Bryn Mawr College