I know that colleges look at one ACT composite score. My question is: Can you take the best section scores from different tests and send those to colleges to create your best composite?
Not exactly. Some colleges do superscore the ACT in the way you're talking about, but you have to send them score reports for all of the ACTs you've taken. Then, the school notes your the highest scores for English, Math, Reading, Science (and Writing, if applicable) and averages them into a superscore composite. For more on what this looks like, we have an article on the PrepScholar blog about how ACT superscoring can be used to shape your test-taking strategy.
There are also other schools (like some of the UC schools) that take the "best sitting" score, which means that they look at your best composite score from one testing instance, rather than your superscored composite. Make sure that you know what the college means when it says that it "superscores" the ACT before you go ahead and send multiple test score reports to them - it'll save you headache, hassle, and money.