An artist needs to create a progression from warm grey to cool grey. Which process is correct?

Correct answer: Gradually reduce yellow-orange and increase blue in warm grey

The governing concept is colour temperature progression within neutrals. Yellow-orange gives a warm bias, while blue gives a cool bias. Therefore, reducing the warm component and gradually increasing the blue component moves each successive grey from warm toward cool without merely changing its lightness. Keeping grey identical creates no progression; changing only black or white changes value, not temperature. Thus option A is correct.