DARK RED: above 150mm aperture. Offers extreme contrast above 200mm. Provides very high contrast of the Moon, polar caps of Mars and it's an excellent choice for observing Venus at daytime as it blocks blue, so the sky appears black
RED: same as dark red but for apertures above 100mm: Moon, Mars and Venus at daytime
LIGHT RED: recommended from 60mm aperture, for very high contrast of the Moon and for the observations of the polar caps of the Mars (from 100mm aperture)
ORANGE: from 80mm aperture. Reveals details of the atmosphere of Saturn and Jupiter or with larger apertures even some details of Uranus' atmosphere.
DARK YELLOW: from 120mm. Increases contrast of surface features of the Moon, clouds of Mars and reinforces atmospheric structures of Jupiter (i.e. Great Red Spot).
YELLOW: same as dark yellow but from 80mm aperture. Very good for observing the Moon (reduces blue chromatic aberration of achromats, thus increases contrast)
GREEN: from 60mm. An important universal contrast filter. Strong enhancement of surface features of the Moon. Very good for low magnifications. Enhances reddish structures in the Great Red Spot on Jupiter. Also good for Mars and Saturn.
DARK GREEN: Same effects as as green, but from 100mm. White spots in Satrun's atmosphere represented better from 200mm aperture.
LIGHT BLUE: from 50mm. An important universal colour filter for small telescopes. Brings contrast enhancement to many solar system objects.
BLUE: from 70mm. General contrast strengthening for the Moon - away from the terminator. Very good for increasing contrast in the bands of Jupiter and Saturn. Good for comet hunting: enhances the contrast of the tail.
DARK BLUE: from 100mm, but ideal from 150mm aperture. Same as blue.
VIOLET/PURPLE: from 150mm aperture. Enhances the dark clouds in Venus' atmosphere, highlights the structures in Saturn's rings and it can even be used for Mercury with very large apertures...
Grey (neutral density): Moon and Venus, also used in Herschel Wedges or in conjunction with Astro Solar Safety films (front cover for all types of telescopes) for solar observations. Generally used for reduction of brightness.