It can be a hassle reprinting games just because the colors aren't what you expect. Whilst the "proof" preview helps, it can't replicate a printed color.
TGC Color Preview contains a deck of 18 double-sided cards showing a set of 36 optimally visually distinct colors so you can see how they will look when printed.
Each card has its RGB and hex color value printed on the card in both black and white text, so you can easily recreate the color in your favorite graphics software and also see which colors work best with text.