CMYK Dullnesss

What kind of printer is being used to output the print job? Desktop inkjet, laser printer, bigger office laser printer, large format printer, etc? Does the printer have extra inks, such as Light Magenta and Light Cyan to extend color gamut levels? Those factors should determine whether to use CMYK or RGB (and certain specific color profiles).

In any case, it's impossible to print colors across the entire RGB color model. Even printers with extra ink colors have their limits. The RGB color model is based on light, or additive synthesis, -such as the light being emitted by a computer monitor. All colors joined together create white. All printing is done using substractive synthesis, laying down varying amounts of ink to filter or hide light reflected from paper or another kind of print material. A "rich black" can be created by mixing a formula of all printer inks together (without going over the total ink limit of the print media being used).

simcha,

Depending on your options, you can also look into this, the entry headings showing the terms and overall concepts,

https://duckduckgo.com/?q=XCMYK+CMYK+OGV&t=ftsa&atb=v320-1&ia=web

Apart from mixing appropriate colors you could also print using spot colors (depending on the printing process this is possible or not). Some printers accept RGB files and the result might get slightly brighter. Talk to the printer about that.