In computer graphics there are 2 main color modes: RGB and CMYK. RGB (red-green-blue) refers to the primary colors of light, and is used primarily video and web based graphics (as televisions and computer screens use light to produce images).
CMYK (cyan-magenta-yellow-black) refers to the primary colors of ink used in printing. As playing cards are printed material, CMYK color mode should always be used. While you can print RGB images in CMYK, there is large variation between what you see on screen and what is printed.
I just wanted to let you know that everyone was great in producing the Custom Playing Cards for a fundraiser. There was a short amount of time where I need the cards in hand and your staff came through delivering them on time. The cards look great and I will be using your company for future orders. -T. Dennis