The Theme Designer rocks. There are GUI adjustment / selection wizards, for dozens of theme objects, in any given blog. You can make font and color changes, using various GUI wizards - and see results, in real time. And the wizards are logically grouped, by function. If you know what objects you need to change, you can tweak your blog theme, without worrying about CSS coding. But depending upon the browser zoom level, some of the available wizards may not be immediately visible, on some "Advanced" submenus.
What Blogger won't tell you