[ItzWarty]

The camera doesn't see like you see. Depending on lighting, an orange ball might appear light orange or even yellowish tanned. The ball might even become red-megenta for worse lighting conditions.

Unless the ball is way far from red on the color spectrum (in other words, it's green-blue), I doubt judges would be so happy, especially since many teams will likely be taking advantage of image processing this year.
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Rule book time:
R08: Robot parts shall not be made from hazardous materials, be unsafe, cause an unsafe condition, or interfere with the operation of other Robots.

C. Any devices or decorations specifically intended to jam or interfere with the remote sensing capabilities of another Robot, including vision systems, acoustic range finders, sonars, infra-red proximity detectors, etc.(e.g. including imagery on your Robot that, to a reasonably astute observer, mimics the Vision Target)