I would color this page in vivid oranges, yellows, and purples to create a fun and spooky feel. Mickey Mouse in the center should be highlighted in bright pumpkin shades, while his rake and candy basket should be in bright orange and yellow. The other characters should each be in their distinctive costumes- Donald Duck in greens and purples, Goofy in white and shades of grey, Pete in deep reds, Chip in yellow and white, and Dale in browns and oranges. The background should be painted in a gradient of bright oranges and yellows, however, the "Happy Halloween!" heading should stand out in bold orange. This should create an enchanting, fun and spooky look that will capture the attention of any audience.