My favorite tape for attenuating bright or annoying LEDs is ruby litho tape (3M Lithographers Tape 616). It passes deep red light and dims bright green and blue LEDs to a faint red. It's perfect for green/amber status lights; the green "OK" is mostly blocked and the amber "Problem" shines through. Removes easily without leaving a mark.
https://www.3m.com/3M/en_US/p/d/b40068069/
https://www.amazon.com/3M-Lithographers-0-375-width-length/d...