I have sent "bright and colorful" RGB files, but these colors look different in the printed version, how is this possible?
As normal, the RGB files will be converted to the CMYK (Cyan, Magenta, Yellow, blacK) color space for the print process. The CMYK color space has a far smaller "gamut" than RGB, and hence it is not possible to accurately produce all RGB colors in print (CMYK).