Dramatic light: Red filtered B&W sky

In ancient times, when Pan-F and Tri-X roamed the planet, clever B&W photographers used a red filter to darken blue skies. This made for startling landscape images. It's impractical to carry a red filter with you today when you can achieve the same result by using your editing software to do a color (channel) separation of your image. This technique gives you three different B&W photos, one if which looks like B&W shot through a red filter. Find an image full of REALLY blue sky. Learn how to create a color separation. Show us the red filtered result.