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:
When you view a preview or proof of your design in PostPilot you are viewing a JPG version. Colors may still be slightly off in the interface. With that said, when PostPilot goes to print your designs we generate high-resolution PDF files and color profiles will be an accurate representation.
If you want to really geek out on color spaces, check out Wikipedia here.