If a color change occurs when two solutions are mixed is it true that a chemical react has probably taken place?

Ms. sullivan's class is designing a miniature roller coaster. after first setting it up, they find that it didn't have enough speed to go through the loop de loop. instead of taking out the loop, they decide to increase the height of the first hill the coaster goes down, and this adds the speed needed to make it through the loop. what would be a drawback to this plan in real life? a) no one likes loop de loops. b) there is no downside to this plan. c) a higher hill means a scarier ride. d) a higher hill takes more time and material to build.