I am posting here with the BBCode disable (you check below the draft message to select this) so that I can describe it to you.
You open and close the color and size using the following, with the text in the middle. I find just remembering these and typing them to be easier than using the buttoms aboveon the draft. Would look something like this:
This is a test for Ron.
You must open the code, type your text, then close the code using the / in the brackets as shown above.
Best is to play with what you want, then hitting preview to see how it turns out. Made changes as needed, then submit when ready. I did this quite a few time suntil I got it right.
Lets see if I remember...click the check box where it says default for font colour. You'll get two sets of brackets. place your cursor between the two and type your message or sentence, or word. Then Highlight what you want to make bigger, use the check box by font size and select your size. This should place your highlighted area between the brackets. Preview and see if it's how you want it. Now to see if I know what I'm talking about.