It's easy to access others' themes and to input these colors as aspects of your Prezi, and similarly simple to alter themes to your own preferences.
Using Existing Themes
By default, Kuler's home page displays the highest rated themes added by users in the last 30 days. Navigate through the themes with the arrow buttons located below them.
You can alter the selection of themes shown by instead clicking "Newest," "Most Popular," or "Random" in the left side menu and adjusting the time frame by accessing the pulldown menu located to the right of the word "Themes."
Click the color bar representing a theme you like, and then click the box with sliders on it that appears in the upper right corner of the information section as shown below.
On the resultant page you will find RGB codes below each color, and you can plug these numbers into Prezi's Theme Wizard as described here. to use them in your Prezi.
Editing Existing Themes
If you should wish to edit the colors within this theme, you have several options by which you can do so.
To adjust the hue of a single color, click and drag the three sliders beneath it or click and drag the highlighted circle in the color wheel.
To adjust lightness/darkness, click and drag the slider beneath the color wheel.
You can also shift all the colors by applying a selected "rule" based on algorithms. Kuler assigns your middle tone as a static base color relative to which the other colors will be changed. Select a different color to serve as your base by hovering your mouse over it or clicking it, and then click the "set as base" option that appears above it. Note that in this way you can also choose to remove a color entirely from your array.
Now choose a rule to apply from the menu provided to the left of the color wheel.
Below are some examples of how your theme will change based on this selection.
Note how in each instance the other colors alter with respect to the base color. You can make adjustments at any time with the sliders or the controls on the color wheel, but be aware that in each case all the colors will be altered; it is only in custom mode that you can edit each color individually.
You might wish to make a note of your initial RGB codes and perhaps also those generated as you go. RGB codes are the numbers underneath each color indicated in the below screenshot. You cannot undo your changes as you alter your colors, and should you wish to revert to earlier selections you can simply plug those numbers back in.
You will also want to make note of these codes when you have arrived at your desired theme. Plugging these numbers into Prezi's Theme Wizard as described here, which allows you to assign these colors to various elements of your Prezi.