By default PostPilot uses the RGB color space in our color picker. RGB was created for colors on the monitor screens which use pixels.
Some RGB colors that are displayed on a monitor cannot be printed on paper -- mostly really bright greens, blues and pinks. That's why in printing, the CMYK color space is used.
Below you can see the color spectrums of both RGB and CMYK:
If you prefer, we make it easy to work directly in the CMYK color space if you need to.
When you view a proof of your design, you'll see an accurate representation of how your design will print.
If you want to really geek out on color spaces, check out Wikipedia here.