out of these three colleges : duke, rice, or Vanderbilt. whic has the least amount of racial issues?

I easily found this 2017 photo of Phi Lamb sorority at Vanderbilt - note the numerous Black and Asian ladies:
https://admissions.vanderbilt.edu/insidedores/2017/07/cc-phi-lamb/

In the 2016-2017 school year, 42% of Vanderbilt students were members of Greek organizations. If one is of the personal opinion that Greek organizations at the school aren’t inclusive enough, then don’t join one. You can always find many diverse friends among the 58% that have no Greek involvement.
https://www.vanderbilt.edu/greek_life/about-us/

Houston’s supposed diversity doesn’t mean things are all peace, love and kum ba yah in the city. 302 murders in 2016, a 50% increase over 2011 - driven by the enormous gang and drug problems in the city:
https://www.click2houston.com/news/houston-murder-rate-remains-at-5-year-high

Houston 1 of 3 cities driving national murder rate higher, report says:
https://www.click2houston.com/news/investigates/houston-1-of-3-cities-driving-national-murder-rate-higher-report-says