Answer:
The Fourth of July parade included the following floats, which all had a patriotic theme<u>:</u> marching bands, clowns, jugglers, and other circus performers<u>;</u> and antique cars, trucks, and other vehicles.
Explanation:
Colons' function is to introduce an item or a series of items when they are preceded by a complete thought (sentence), such as it is used in the sentence "The Fourth of July parade included the following floats, which all had a patriotic theme:" which it's a complete thought.
As for commas, one of their functions is to separate items in a list such as in "marching bands, clowns, jugglers, and other circus performers".
Likewise, semicolons can also be used to separate items in a list when the list items already contain commas. In this case, semicolons are used to show which items are grouped together, and to outrank the existing commas, such as it is employed in the following list: "marching bands, clowns, jugglers, and other circus performers; and antique cars, trucks, and other vehicles." Here, the semicolon works as a separator of the two lists.