Google's John Mueller was asked if swapping out your logo on your site for the site's birthday with a special birthday logo can hurt your SEO. John said on Twitter "I've never seen issues around that." In fact, Google does it all the time on its home page and heck, I swap out the theme on this site for special days as well.
John did add "not that it's a model of perfect SEO" to swap out your logo, "but Google Search's homepage changes logos very often too," he said.
Just the other day we had a special theme on this site for Flag Day in the US:
I do it all the time on https://t.co/05SyOtLMkv - today is Flag Day in the US pic.twitter.com/iR5vUf8ES3
— Barry Schwartz (@rustybrick) June 14, 2022
Here are those tweets on Twitter:
I've never seen issues around that (not that it's a model of perfect SEO, but Google Search's homepage changes logos very often too).
— 🐝 johnmu.xml (personal) 🐝 (@JohnMu) June 14, 2022
I really do not see changing the logo for a day or so, or even some color scheme themes, hurting your SEO or rankings in Google Search. I am sure there is a way to do it where it can blow things up in a bad way, but in general, it shouldn't negatively impact things if done right.
Forum discussion at Twitter.