When you login to multiple Google Accounts on your browser, Google links them all on the client side. If you want to sign-out of an account, this unfortunately isn't supported by Google. You'll need to log out of all your accounts and sign back into the one's you want to again. This is for security reasons.
I haven't even found any workaround to this. Tedious but true.
Suggestion: Use incognito instead. If you want to sign into multiple account, instead of using the same browser instance, open the incognito and login to another account from there. So you can only logout of that account.
Hope this helps! If you have any other suggestions, mention in the comments below.