定期的に変更されることも多いので、リンクだけまとめています。

Google

https://about.google/brand-resource-center/brand-elements/

X(旧Twitter)

https://about.twitter.com/en/who-we-are/brand-toolkit

https://about.twitter.com/ja/who-we-are/brand-toolkit

Facebook

https://about.meta.com/ja/brand/resources/facebook/logo/

Youtube

https://www.youtube.com/intl/ALL_jp/howyoutubeworks/resources/brand-resources/

Instagram

https://about.meta.com/ja/brand/resources/instagram/instagram-brand/

LINE

https://www.linebiz.com/jp/logo/

Pinterest

https://business.pinterest.com/ja/brand-guidelines/

Tiktok

https://developers.tiktok.com/doc/getting-started-design-guidelines/