Quote:...At this point those white areas are as much a part of the image as anything else. Aren't they?
Not when printed. As before there is no white ink.
White = colour of the paper.
How far off-white before there is a tint. Probably not very much. I will let you do the trials.
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Ok before I pack in for the night. This is how I might do a simulation of a print on an off-white paper.
Using Color-to-Alpha, pick the opacity threshold from the image to get as close to original as possible. https://imgur.com/8Uvds0W.jpg
An underlay with the 'proposed' paper color. https://imgur.com/YgXEn3B.jpg
Flatten the image. Using the colour picker tool and the info window check a white area. https://imgur.com/5ThRBgn.jpg
How much of the colours are used? A smattering of red & green and a bit more of blue. But this is a RGB image, once it gets translated by the printer to CMYK then expect some change.