"Makes a Rainbow" is the seventh episode of season three and the thirty-third episode overall of the animated children's series The Magic School Bus. It originally aired on October 26th, 1996.
Ralphie wonders why rainbows are always red on the outside and violet on the inside. Dorothy Ann comments that it's the prettiest combination: red, orange, yellow, green, blue and violet. Arnold answers Ralphie's question saying that the colors come out according to the length of the light waves with red being the longest and violet the shortest.
Arnold baffles the class, and Wanda asks since when did he know so much about color. He tells her that rocks and color are his two favorite things. Carlos creates his rainbow out of flashlights and colored candy wrappers claiming it to soon to be everyone's favorite thing while Dorothy Ann scoffs at the idea of Carlos making a rainbow out of light when he needs color.
Carlos then completes his rainbow but the red light makes it appear that he's ruined D.A's project. When she demands to know what he did, he says it looks better this way. She insists that how it was before was correct and pulls out a violet research book to prove him wrong. He laughs at it because it's purple while she retorts that it's violet. Their quarreling is quickly stifled by strange noises coming from Ms. Frizzle's closet. They go inside to find her playing a colorful pinball machine. D.A remarks that it looks like she's making a rainbow too while she says she trying to but quickly fails.
Devastated Ms. Frizzle despairs that she'll never make the rainbow. Ralphie observes that he's never see a pinball machine like this one to which she perks up and says she built it herself with Liz's glowing guidance of course. She tells the class that instead of steel balls one plays with white light and tries to make a rainbow. Keesha quickly remarks that rainbows are all different colors and asks how one would make a rainbow out of white light.
Ms. Frizzle tells her that that's an excellent question and that if she makes a rainbow they keep the machine but if they lose it'll be taken away. The class quickly volunteer to assist but D.A remarks that Carlos would be useless as he knows nothing about color but he says that they play with light pulses. Ms. Frizzle breaks up their argument and sends Liz and everyone except Arnold into the bus. Liz then shrinks it and they fly into the classroom where Ms. Frizzle tells D.A and Carlos that they're in charge, much to D.A's disagreement.
The bus then shoots into the machine by turning into white light. Ms. Frizzle then explains the mechanic of the game to the class: They have six light pulses to get the light into the eyes to create the rainbow. When Ms. Frizzle activates the pinball machine, the colors bounces around and dissipate. When Keesha asks where all the colors came from, Ms. Frizzle shows the class a replay screen that shows the white light bounce off the mirror and go through the prism, thus making the colors come out. Carlos argues with D.A. and tells her that it was colored light that came out of the prism. Ms. Frizzle also adds that the class could get the same colored light when they get it in the same colored eye. Arnold learns that the class needs to get the colored light bouncing off things until it hits the white colored eye and scores. So Carlos decides that the class should bounce the red light to the mirror to get it inside the red eye. As the class tries to complete the game, Arnold discovers that Mr Rhule, the principal, has made his way inside the classroom.
Arnold distracts Mr. Rhule and the class attempts to finish the pinball game, successfully getting the red light through the red eye using a red tomato and a mirror. Arnold, meanwhile, tells Mr. Rhule that Ms. Frizzle is in the library and the principal leaves the classroom to find the teacher there. Back in the pinball game, the class then uses the orange light, only to have it disappear once it runs into a green shamrock, causing it to turn green and bounce off one of the mirrors to enter the green eye. Carlos attempts to get D.A. to acknowledge her supposed mistake and the class watch the replay as the orange light bounced off the mirror, hit the green shamrock, and disappeared. D.A. then surmises that when someone sees something green, it's because it is green light that enters their eyes. The class decides to sink two colors at once since they only have three more chances to make the rainbow of the game. Phoebe suggests orange and blue since they blend well together. The class agrees with this and uses Carlos' sweatshirt for the blue light to bounce off of it. They successfully get the orange inside the orange light, but Carlos, who was hesitant to have the blue light bounce off his sweatshirt, ducks away from the blue light as it comes towards him and it disappears into the yellow bus. D.A. then tells Carlos that there needs to be something blue to bounce the blue light.
Meanwhile, Arnold is still trying to keep Mr. Rhule inside the library. When Arnold tells him that he missed his snack, Mr. Rhule decides to look for Ms. Frizzle inside the cafeteria, Back inside the pinball game, the class has three more colors to go, but only two light pulses as well before they fail the game. D.A. decides to use both blue and yellow at the same time, using the bus to bounce the yellow light off of. The yellow and the blue light successfully enters the eyes of their colors and all they have is violet to go and the game is over. Ms. Frizzle activates the violet light and D.A. uses her book to bounce it off and into the violet light. The class return to the bus to exit the pinball game, only to find that they are trapped inside.
Mr. Rhule, enters the classroom and Ms. Frizzle exit the closet just in time. Arnold enters the classroom and gives an idea for the class to turn the bus into light. but this only transforms the bus into six different buses of each color of the rainbow. When D.A. learns that the prism the bus bounced off of splits white light into different colors, she surmises that the class would be mixed together if they went backwards through the prism. Arnold flips the buses backwards to the prism and they escape out of the game. The class returns and learns that all the colors are made by ordinary light and the prism is what disperses them, thus creating a rainbow. By the end, they learn that Ms. Frizzle and Mr. Rhule had a bet over the machine, but since she lit up the colors, she gets to keep it. He is disappointed, but she lets him play a game.
- When the kids are looking at the machine and Ralphie is amazed, it skips to the scene where he says "Duck!"
- When Carlos says, "Dorothy Ann! It's coming right at you!", the blue color in the rainbow is out.
- This is Mr. Ruhle's first appearance.
- Arnold doesn't say "I knew I should have stayed home today" in this episode.