<prompt> Most commonly used colour of the filter used in darkroom safelight is:BlueRedGreenYellow  <response>: X-ray films are very sensitive to the blue-green region of the spectrum and are less sensitive to red wavelengths. The red GBX-2 filter is recommended as a safelight in darkrooms where either intraoral or extraoral films are handled because this filter transmits light only at the red end of the spectrum.Film handling under a safelight should be limited to about 5 minutes because film emulsion shows some sensitivity to light from a safelight with prolonged exposure. The older ML-2 filters yellow light are not appropriate for fast intraoral dental film or extraoral panoramic or cephalometric film. Reference: White and Pharoahs Oral Radiology Principles and Interpretation 7th edition page no 71 