How do I show colleges that I have an interest in Spanish culture?
Take Spanish.
Join Spanish Honor Society
Join/Form International Clubs
Do an exchange year in a spanish speaking country
Can you think of anything outside of school that I can do?
Who are you showing this interest to? Colleges? Why?
If you are going to major in spanish, you should be doing those things I mentioned.
If in general and you are going to apply as a Hispanic, then you don’t have to do anything.
My daughter volunteered at a Latin American Association in our city. She helped teach a basic computer course to Spanish-speaking adults and helped at a special event. They had tons of volunteer activities available. She also helped read books in both Spanish and English to little kids through another volunteer group that met at a Latin American shopping center on weekends. At school she was involved in the Spanish National Honor Society. There were countless ways to get involved with Spanish speakers and Latin American culture at her school and in our city.
You may not be living in a place that has so many opportunities, but there likely are some if you look. Do some searches online for local volunteer (or employment) opportunities that require Spanish. Find out if there is a local Spanish language newspaper and read the articles and advertisements for ideas. Ask the Spanish teacher at your school (or other schools) for suggestions.