For screen printing, the choice of a printing color is very precise. We use Pantone references (explained here) to print your order in the exact colors of your choice.
To do this, you must provide us with the exact references desired for your order, via a Pantone paper book.
If you do not have such a book, you can use a page like this one:
http://www.toutes-les-couleurs.com/nuancier-pantone.php
keeping in mind that a color on screen will not be identical to the print color.
If you only give us the name of the color (example: yellow, mauve, navy blue,…), we will use the reference color for this same color. However, there are many shades for each color.