Back in the day of Black and White silver based photography one would slap on a real "RED" filter, deep red no less for a variety of reasons. For landscape photography it lightened the yellows and reds of flowers while making the blue sky and green foliage darker. You did this in particular when you wanted to accentuate the sky and get better cloud detail. With portraiture it tended to help lighten the skin and even out the complexion. Obviously I went for cloud detail today.
Of course, I shot with RAW/Jpeg combo. The RAW images have all the detail and colors there just in case I get a wild hair and want to do something with them one of these days.