Freewell Grey Filter 3 stops Neutral density (or ND) filters (5 Grams) : Produce a grey neutral tone and are used to reduce light, enabling more control over exposure and depth of field without affecting color contrast. These filters are clear in the bottom half of the filter with a gradual transition to the ND effect in the top half. They are primarily used for light reduction in skylines of landscape shots.
Freewell Orange Filter 1.8 Stops(5 Grams):, Perhaps its a normal evening, you can see a fair view and its a nice enough scene. So how do you improve, well you could add an orange grad to colour the sky, perhaps a coloured streak across the image over the sun providing a sunset effect, perhaps you could use an ND grad to hold back the sky area, allowing the land to be lighter and more colour saturated.
Freewell Blue Filter 1.8 Stops(5 Grams):grad filters create a realistic cooling blue effect. It enhances the blues of water and skies and is a vital tool in your landscape filter armory. Soft edge grads have a smooth transition from clear to the color.