Could someone explain the difference in using colored filters for black and white photos? What is the best practice using these filters for portraits, landscapes, macro? For different types of weather: sunny, foggy, morning, evening, and so on?
If you are using a digital camera, there is little need to use colored filters, as you can apply their effects in post processing when you do the black and white conversion.
If you are shooting film, then
Different filters will change the threshold of black and white. For example, a yellow filter will make the more yellow colors black. You can use these filters to enhance different parts of a B&W image.
The easiest way to remember the effect of a filter is this: A filter lightens its own color and darkens the complementary color. Here is a link to a color wheel that illustrates the concept. Colors 180 degrees opposite are the complements.
So, from the color wheel, we can learn that a green filter will lighten some foliage (foliage does not read completely green, but green-yellow), and darken reds (some complexion contains red -- be careful because this may make skin complexions a bit blotchy for people with ruddy complexions).
The red filter is the "landscape filter" because it tends to produce dramatic skies -- the dark sky against white cloud or snowy peak effect that is so appealing in black & white images. It lends a slightly ghostly effect to green foliage, particularly evergreens.
I've attached some simulated B&W effects on an image that includes sky, foliage, and clouds. This is simulated using NIK Silver Efex, so it's not exactly like using glass, but it's darn close:
Original As Shot in Color