I've been experiencing with my editing techniques lately. While, I don't do any major retouching I love to add contrast & color. Since I shoot in RAW, I also tweak the exposure and color temperature, and work with the contrast and color filters using GIMP. Here are a few samples of editing from my most recent shoot. On version left is the original jpg image, a little bland for my taste; and on the right is my edited version.
The technique is really simple and I like how it dramatically changes the mood of the image. You just take a solid color layer in front of the image, select a layer mode, and adjust the opacity. I use a variety of colors: Purple (#ac65b3), Blue (#509aff), Orange (#ff6400), Green (#006644), Yellow (#f3d355).
To vary the effect adjust the layer mode: multiply or overlay will add the color to the image, screen will add color and slightly wash out the image, and subtract will remove that color from the image. I find that the subtract filters are the toughest to work with but I usually use them with a green layer to add some red to warm up the image.
For this particular shoot with Rosemarie, who recently moved to San Diego from Cuba, I liked how the warm colors fit in with the sunset. Clouds kept interrupting the sunlight forcing me to use a flash so it helped to bring back what was lost of the natural light. I also tried cooling down some of the night shots but couldn't quite get the feel of it. I think I'll need to experiment with new filters for that. I should get another chance at a nighttime beach shoot soon though, hopefully while the moon is still full.