Couldn't stress also be a synonymous with changes to the surroundings that cause the plant to adjust? Some amount of stress I think is a good thing, and that is debatable. Natural dormancy some plants benefit from, even though they discard all leaves, and are unable to photosynthesize well for months. Watching for stress indicators can certainly help us to notice that the plant is reacting to these changes.

Thanks for the info about red leaves. I first noticed this when I bought an indoor plant, and as soon as I walked with it to the parking lot the leaves blushed. I thought I would have to live with a red plant, but eventually it greened up. It still changes to red on the windowsill on very sunny days.