These are the colours used.
RGB (Red, Green, Blue) – These are the primary colours of light which are best used for screen.
CMYK (Cyan, Magenta, Yellow, Keyline Black) – This colour spectrum is 4 colour which lends itself to full colour printing.
Converting all your artwork for printing from RGB to CMYK gives you more control over the final result of the colour. When we receive your artwork it is automatically converted to CMYK by our software. If it uses RGB, this gets changed to CMYK, but this may result in printed colours that are slightly different to your expectations. We can not be responsible for this and you should submit your artwork in the CMYK colour format.
Remember that all files should be prepared in with CMYK colours. If you are designing your own artwork, be sure to convert colours from RGB format to CMYK. There is usually an option in your graphics package to do this.
A professional designer will ensure the working space is set to CMYK from the very beginning.