To blend the colors of transparent objects on a spread, InDesign converts the colors of all objects to a common color space using either the CMYK or RGB color profile for the document. This blending space enables objects of multiple color spaces to blend when interacting transparently. To avoid color mismatches between different areas of the objects on-screen and in print, the blending space is applied for screen and in the flattener.

The blending space is applied only to those spreads that contain transparency.