A little dirty secret about the PMW-EX1 and EX3 cameras was that they were a little eager to boost reds in certain black materials, turning some black cloth brown or maroon. There’s a long story behind it, well told and clearly explained by Art Adams, but what people will want to know is ‘how to cure it’. Short answer, get a Tiffen T1, but Art’s article explains far better:

Tiffen Goes Into Production on T1 Far Red Filters, by Art Adams | Cinematography