Many colleges use red and gray as part of their color scheme, though rarely as the *only* two colors. It's difficult to give a definitive list without specifying what constitutes "school colors" (primary, secondary, tertiary, etc.). Some schools might heavily feature red and gray while others use them more sparingly.
To find colleges with red and gray, it's best to search online using terms like:
* "Colleges with red and gray school colors"
* "University school colors red and gray"
This should yield several results, allowing you to check the individual school's official website to confirm their color palette.