The removal of Red Filter from Silhouette Challenge videos on Tiktok is not possible. This is because the effect / filter applied is quite aggressive and irreversible. It darkens the subject, keeping only the outline visible, and applies a red color to the background. So one can only see a shadow form of the original dancer or performer.
Trying to reverse the aggressive color and light filter is impossible. Most of the information from the image is lost because of the red filter. So it cannot be reverse engineered. Even if there are AI tools claiming to remove the Tiktok Red Filter, they are most like scams. They may be trying to add malware or viruses to people's smartphones and laptops. Or they will be paid third-party apps or plugins, which will only cause you to lose your money.