Classical Western astrology is based on the movement of the seven planets within the zodiac: the Sun, Moon, Mercury, Venus, Mars, Jupiter, and Saturn.
In accordance with the Law of Seven, the organizing principle of the universe, the seven planets correspond to the seven qualities found in the seven metals of alchemy, the seven colors, the seven musical notes, the seven archangels, the seven cosmic rays etc. Seven is the Law of the Octave, repeating itself over and over but on higher levels.
Observing some of the basic qualities of the seven primary planets in astrology gives us a way to understand the Law of Seven itself, and how it manifests in other phenomenon.
Temperatures of the Seven Planets
The Sun is hot and the Moon is cold.
Mars is hot and Venus is cold.
Jupiter is hot and Saturn is cold.
Mercury is neutral and can be any temperature.
Colors of the Seven Planets (from William Lilly)
The Sun is gold or orange, and the Moon is silver, light-blue or white.
Mars is red, and Venus is green or light-green.
Jupiter is green, purple or chalky-white, and Saturn is black.
Mercury is yellow, blue, green, pink or mixed.
Energies of the Seven Planets
The Sun radiates, shines, is stable, and the Moon receives, reflects, fluctuates.
Mars drives forward, directs, penetrates, and Venus harmonizes, accomodates, balances.
Jupiter expands, spreads, transcends, and Saturn contracts, astringes, crystallizes.
Mercury bridges, communicates, oscillates.