It's not. It violates 3d
I wish I knew this before trying to compete in square-1 for the first time. I was using a stickered volt and the yellow stickers had a weird problem with the adhesive and half of them would constantly fall off, and I just reapplied them with a glue stick. That worked for a while but eventually, I had enough. I figured since people use a black side all the time, I could just not have stickers on a side to make it black. Unfortunately, I wasn't able to compete with my volt. I was the only person in my group at the time that actually did square-1, so the only other option I had was to use my friend's super old and janky shengshou.
Crazybadcuber made a video where he used rit dye to turn a stickerless zhanchi into a black one. However, I'm not sure what the piece design is on the Tornado. If it's a capped design it should work fine, just do the colored parts and not the black internals. But if it's all one piece and cannot be separated then your not going to be able to get away with using this method since it uses some chemicals that can harm the magnet system.
(Ignore the title this was made before stickerless cubes were made legal in the WCA)