Colours with an asterisk denote that the colours can be color1, color2, color3, and color4, with the original colou0 being equal to color1. Gray has 100 variants. A list of colour codes can be found here.
Colors were visual properties that derived from the light spectrum. Colors were often culturally significant in the galaxy.
In the time of the Old Republic, red was prominently displayed as a symbol of diplomatic affiliation, and that's why many ambassadorial capital ships were painted so. Any consular ship hailing directly from Galactic City was colored red all over its hull, while others would only bear stripes in that hue. When the Empire rose, some of those habits were seemingly kept in use, for what was called « Republic red » followed the teaching of seemingly co-opting the republican traditions. The Emperor's personal guard and most features in his private apartments or in the Imperial Palace were crimson as well.
Color blue was associated with chancellorship in the waning days of the Republic, and lavender drapes are known to have hanged out in the Grand Convocation Chamber. Chancellor Finis Valorum and Senator Palpatine would often adorn blue coats or robes to express their interest in leading the Republic. Palpatine's New Order didn't make wide use of blue.
A light medium grey was the traditional hue the Empire chose for its ships and stations. The aim was to make the imperial presence recognizable at glance, and to instil fear by insisting on the weapons' power and not on their appearance. Though some distinctive unit markings did exist, they still were marginal.
While color white was associated to the Force by some (i.e. the White Current of the Fallanassi), it was also chosen by the Empire for its elite force of stormtroopers. Their full anonymous armor was designed by designers who knew that what people couldn't see was more terrifying than what the Empire could do.
The reptilian Tarasin from Cularin used to express their ideas or emotions through a complex system of skin color changes. For example, their light green skin changing to purple indicated amusement. Though much of their Tarasin Skintone Language actually couldn't express complex series of thoughts, the changing colors of the skin could be used to give basic directions without speech while the Tarasin were hunting or attempting to evade the massive kilassin that roam the jungles of their homeworld.