I am using the Console Jekyll theme, but have modified a few things such as colors.
For the theme modifications, I think I've only changed the file _sass/_dark.scss. I've also added _layouts/research for my purposes.
Install requirements: https://jekyllrb.com/docs/installation/#requirements
Build and run locally: https://jekyllrb.com/docs/
# install gems
bundle
# update
bundle update
# serve and live reload
bundle exec jekyll serve --livereload