Can I make one of the tabs in a group on the left of CMSB a simple external link?
Can I make an external link in an editor for an admin somehow?
Basically, I want to link a color picker website for an admin to visit the site and grab a hex code:
For the left-column menu, try the Modify Header Links plugin:
For a link on the editor page, when setting up the editor add a URL in the "Section Description" WYSIWYG at the top.