What are the lights used backstage as working lights called, which typically remain on during blackouts?

The lights used backstage as working lights, which typically remain on during blackouts, are known as "blues." These lights provide sufficient visibility for stage crew members to navigate safely in dark conditions, ensuring that they can perform their tasks without interference or hazards. The use of soft blue light minimizes the intrusion on the audience's experience while allowing backstage personnel to move effectively without causing distraction.

In contrast, footlights are positioned along the front of the stage to illuminate performers from below, while striplights are long, narrow fixtures that provide wash lighting, often used to create various effects on stage. Spotlights are focused lights used to highlight particular areas or performers but do not serve the same functional purpose as working lights backstage. Therefore, "blues" is the term that specifically refers to the essential backstage lighting that remains on during performances.