Colors are a huge part of tarot reading, the keyword being reading. One can memorize the definitions of a card, but when actually reading the spread and the layout, everything shoudl be taken account for, including the colors, and how they present to you.
This is why I thought I would share this article by Jesse Russels on the history of the color blue, to help give some insight on this aspect.
Blue was once little-known in the Western palette. Homer’s sea was “wine dark”; blue would not be used as water’s color until the seventeenth century. It has evolved from its original association with warmth, heat, barbarism, and the creatures of the underworld, to its current association with calm, peace, and reverie. Like the unruly green, the Romans associated blue with the savage Celtae and Germani, who used the woad herb’s rich leaves for their blue pigments. These northern barbarians also painted themselves blue before war and religious rituals. The ancient Germans, according to Ovid, even dyed their whitening hair blue.