I have an RGB PSD document with 300 dpi resolution. Basically I designed it to print as my business card. When converting this from RGB to CMYK, my original colors are changing. Is there any way to keep the colors intact so CMYK looks exactly the same as RGB?
No, you can’t expect RGB colors to translate exactly to CMYK for printing.
Monitors make colors with light. Light can be any intensity. Ink is made of solid physical colors from things like rocks, which are ground up and put in a medium like oil or latex. You spread ink on paper and it’s never going to be as bright as a color on a monitor.
Offset printing presses use four specific ink colors — CYMK. When they are mixed together, they can produce many shades, but not nearly the type of shades — such as electric green, safety orange, deep blues, and many other shades and intensities — that can be produced by a monitor, or by special chemical mixtures (having nothing to do with CMYK) that create specialized inks/paints.