There are manufacturers who make decorative red contact lenses that can be worn with costumes; however, the lenses sold must be FDA approved. It is illegal for contact lens manufacturers to sell colored lenses to consumers that are non-prescription and unregulated.
Many people enjoy wearing red contact lenses as part of a decorative costume, but unregulated colored contact lenses pose a serious risk of eye injury. The FDA recommends obtaining decorative colored lenses from manufacturers that require a prescription from an eye doctor. This is the best way to ensure the decorative lenses are safe. There is no such thing as safe "one size fits all" lenses. An eye doctor must do an exam and take measurements to determine which type of contacts fit best. Once a valid prescription for contact lenses is issued by a trained eye doctor, it is possible to find a good selection of red decorative lenses from reputable sellers.
The FDA has issued warnings about purchasing decorative lenses from sellers that do not require a prescription. For example, consumers are advised to avoid buying lenses from costume shops, convenience stores and street vendors. Non-prescription decorative lenses may scratch the eyes or cause corneal infection or blindness.