To make a Team Umizoomi Halloween costume, collect materials in the appropriate colors and patterns for the chosen character. For Milli, use a pink floral dress and pink leggings. Try to match the color and pattern as closely as possible to the character. You can make a Geo costume from a blue sweater with an attached hood, and a blue pair of pants.
A Milli costume should include a pink hood with a long ribbon attached on either side. Viewing several pictures of the character during costume creation can help make the costume as accurate as possible.
For a Geo costume, add an orange belt with green and yellow shapes affixed to it. You can also dye your hair blue with temporary dye to match Geo's hair.
You can make a Bot costume by either adding appropriate details to clothing, or by cutting holes for arms, legs and head in a large cardboard box, and painting it to resemble Bot.
If using the clothing method, find a green sweater with an attached hood and green pants. Use fabric paint to paint a picture of Bot's screen on the stomach of the sweater, which includes a blue and white bullseye pattern, outlined in a yellow square. Attach black circular eyes to the hood. Use a small cup and drinking straw, painted with the appropriate colors, to create an antenna, which you should also attach to the hood.