The Tarot Deck colours are an easy way to quickly and accurately distinguish between each tarot card.
Golden Dawn attributions
The Hermetic Order of the Golden Dawn developed a sophisticated system of colour attributions for all 78 cards. “Clairvoyance” was used to verify these colour attributions, but I have not seen any details of how that worked. You can see the tables in Liber 777.
The colour system was based upon the kabbalistic structure of the four levels of creation – Atziluth, Briah, Yetsirah and Assiah, which gives a unique four colour palette for each card.
However, since Golden Dawn teachings were a secret many GD inspired tarot decks omit the system. These cards are from the Robert Wang Golden Dawn deck.
While the designs and symbols are literal expressions of the Golden Dawn descriptions, the omission of the colour attributions cause the reader to focus on the symbols. Recently Pat Zalewski, a modern Golden Dawn Adept, expressed the desire for a GD Tarot deck that incorporated the colour system.
Rider-Waite Tarot and colour
As a Golden Dawn adept A.E. Waite was familiar with the colour attributions, but he omitted them from his designs. However, he kept the odd attribution for a card and included it in his descriptions. As you can see the same shade of grey is used for both the Ace of Pentacle and the Four of Swords, while we similar colour for the background of the Three of Wands and the tomb in the Four of Swords.
Book of Thoth Colours
It is not until we come to a Tarot deck created during World War II during shortages of paper and artistic materials that the Golden Dawn colour system was used.
Here are the same four cards as found in the Book of Thoth.
We see the unique nature of the Golden Dawn system. The importance Crowley attached to it is emphasized by the fact that he included the colour tables in his Book of Thoth.
The main problem with the tables is in nomenclature and reproduction. Standardisation of colours, their tints, tones, etc did not exist until recently, so there was always the need for interpretation. Now we have Pantone of course.
I think you can see where I will be going with my Tarot deck. There is no point in slavishly following the original Golden Dawn scheme as it is impossible to reproduce exact matches, and whatever designs I come up with will be simpler anyway.