Saturn is black/grey. Capricorn is the brown/black/green/earthy tones and that's because if it's triple rulership of Mars (god of war) Saturn (Titan of time/death) and Pan(God of the wilds and it's creatures). Don't try to argue I have a Sun/Moon/Saturn Cosmic trine, Capricorn Mars (Uranus/Neptune/SN). I also have Saturn aspecting Uranus and Pluto.
Note Saturn rules excrement so brown and yellow stem from here. (Libra exalted, Capricorn, Aquarius)
Mars is dark red (like blood, it original ruled Scorpio, it is said to rule Aries, and is exalted in Capricorn)
Venus rules pink, green(maybe yellow). (Tarurs/libra)
Jupiter purple and blue (orange?) (rules sag, Pisces, exalted in cancer)
Mercury rules quicksilver/brown and multicolors (Gemini, Virgo)
Neptune is high octave Jupiter ruling variations of blues. (Pisces, cancer and Gemini/sag exalted)
Uranus is higher octave Mercury ruling multicolors above the natural sorts (Neons etc.) (Aquarius and Scorpio)
Moon rules white. (Cancer, Taurus, Virgo)
Sun Rules yellow/gold (Leo, exalted in Aries)
Pluto bright red (Aries in Sidreal, Scorpio in some tropical, exalted in Leo and Sag/Gemini)