① Blue background: Blue is the most commonly used business color, and the slides with blue background are steady, generous and not lacking in vitality. The sky blue background color is most suitable for matching with white, yellow and light blue foreground objects.

② Red background: The slides with red background are saturated and warm, which is easy to arouse students' emotions. The commonly used red background is Bordeaux.

Dark red, such as rust red, can be matched with white, yellow, orange and light brown foreground objects.

③ Green background: Green is easy to be confused with blue and purple, and it is easy to cause too strong visual stimulation when matched with red. Therefore, when using slides with green background, it is best to use white, yellow or brown as the foreground color.

④ Purple background: Purple can create a romantic effect, but it is not easy to match with other colors. It is best to arrange light purple or white foreground objects on a purple background. If you want to emphasize visual contrast, you can also use yellow, orange or yellow-green foreground. ⑤ Yellow background: The yellow background is bright and tidy. On a yellow background, you can use blue, purple and bright foreground as a contrast, or you can use black and dark gray.