If you need to add texture to a design, check out The Pattern Library. This is a curated collection of patterns you can download and use.
Once you have chosen a color palette for your course, you might want to make use of it in PowerPoint to create some graphics or make a presentation for your students.
One way to create a color palette is to use the color wheel. Adobe has an interactive color wheel at color.adobe.com. You can use the sliders to find a particular color, and then select a color rule to see its complement on the color wheel or the two colors that go along with it to form a triad. You can also generate an analogous, monochromatic, or compound pattern based on the color. (Check out the color theory reference chart to see how those color relationships are formed.)