If you are coming to Katy for the ARTkaty art show and Jazz Fest, you might as well make a day of it and check out this Color in Action event. It won't be as large as the downtown Houston versions, but there is still a possibility of getting some great shots
You will want to use a longer lens and cover your camera with a plastic bag of some sort to keep the fine powder out of your equipment. You might bring a clean shirt and a towel to clean up with if you get too close to the action.
Seven Lakes High School is 18 minutes away from Katy High School and Midway BBQ, so you should have ample time to enjoy both events if you choose to head out early.