There is a big difference between an RGB (additive) and a CMYK (substractive) color space. RGB is used for digital cameras, scanners, screens and is based on light. The more light the 'lighter' (additive color space) . R stands for Red, G for Green, and B for Bleu and these are the basic colors which are used to reproduce all the other colors on a screen.
In a printing environment the necessary basic colors to reproduce all the colors are different. Here you can say 'the more color, the darker'.

We use the basicinks Cyan (type of bleu), Magenta (pink/red), Yellow and Key (basic black). These 3 inks C, M and Y are sufficient enough to reproduce the entire color space so that is why Black is added as a basic color to get a nicely balanced image. 

The pictures from your digital camara (RGB) always have to be converted to a printable CMYK color space using a specialised software such as Adobe Photoshop. It might happen that this conversion causes the colors to fade, but you can always make changes.

Image below: after conversion from RGB information to CMYK (=printresult) 

source wikipedia: http://en.wikipedia.org/wiki/Image:RGB_CMYK_4.jpg

  Below you can see the RGB (additive color space) and the CMYK (substractive colorspace) that wil be used for printing

We can process your RGB files, but you have to keep in mind that the colors (as mentioned above) can get paler. By accepting the preview during the orderingproces you declare to accept the colors on the final printingresult.