As part of the "Customize It" step of the survey creation process, you'll see an appropriately named Survey Appearance box that allows you to alter your survey's appearance. From here you can:
Determine whether you want the questions to be numbered and if you want to include a progress bar at the top of each page. These are turned on by default, since including numbers and a progress bar makes it much easier for your respondents to see where they're at in the process of filling out your survey.
Add your own logo or image to the top of each page. Selecting this option opens our Library, where you can upload new images or choose to use any images you've previously uploaded.
Change the background color and the color of any links included with the survey. Just use the color wheel to the right of the two options to select the colors you like or enter the appropriate HTML color codes if you know exactly what you want.
Change the font type, color and size of your question text (this will also change the font of your headers and comment blocks).
Change the font type, color and size of your answer text.
Note that you do not have to edit the look of your survey at all if you're content with the defaults.