There is a font size, font type and font color tool there.
The icons are immediately above the text box where you type your posts/replies. On my screen they appear above and a little bit to the right of the tools for selecting Bold
formatting. If you hover the mouse-pointer over the tool icon a small text should appear giving you the name of the tool. They should say "Fonts", "Sizes" and the one for color says...uhm well...Colors
Mark the text, then select the font size from the pull-down menu that should appear when you click on the tiny downward pointing arrow next to the tool. Choose say number 5
Oh, by the way, there's no font type and font size tool in the Quick Reply box