I worked on a merchandiser from a client and the photo used had an extra red layer in the cmyk channels palette to color seats and some smaller details of a car red instead of yellow. There was only 1 layer in the layers palette. It seemed that they used a certain red (like you can pick from the color libraries). I was a bit confused because adding an alpha channel usually masks in red as well. So, I wonder if it is possible - but most of all how you do it - adding a color channel. And then... why would you do it there and not in the layers palette. Anyone any idea of how and why?
Maybe worth mentioning...
The photo is a tif file and saving it as jpg results in losing this red channel information, which means that the seats turned out yellow again. That's how I found out that there was an additional 'red' layer in the channels palette.