How to match CMYK with RGB?


I am currently designing a document for printing. I have two strips of colors on the corners of the document, it has the color pallet in RGB but when preview in CMYK it just looks terrible.

I’m wondering if there are any ways to match RGB with CMYK and are there any sites that I can find HEX codes for CMYK.

Thank you.

Note: HEX codes for CMYK is somewhat meaningless.

RGB can be represented as HEX because it has R, G, and B (and sometimes A for alpha) values from 0 to 255, represented as 00 to FF in hexadecimal notation.

CMYK, on the other hand, is only represented as 0 to 100.

It is very important to realise that there are many RGB colours (including those rich glowing purples) that simply cannot be represented in CMYK at all.

RGB is designed for additive media e.g. computer screens. If R, G, and B, are all 255, then R + G + B = white.

CMYK is designed for subtractive media, such as printing, so if all values are 100, C + Y + M + K = black. In practice, that tends to be too wet (too much ink) to use.

In theory, just 100 each of C + Y + M is also black, but the realities of real life printing ink usually mean this comes out a muddy grey or brown.
Likewise, 100 K and 0 (zero) C, Y, and M should theoretically be black, but most real life K inks are merely a dark charcoal grey, so “rich” black is usually represented as a mix of high (possibly 100, possibly not) K and moderate values (around 25-35) of C, M, and Y to produce something close to black on real media.

The colours that each system can represent are known as a colour space or gamut, and the CMYK gamut is significantly less than the RGB gamut:

Source: CMYK vs RGB: What color space should I work in? | MCAD Intranet

Note: these are pure colours, without any black mixed in.
As you can see, your purple colours are not part of the colour space that can be represented by CMYK.

And, yes, there are colours that the human eye can see that cannot be represented in CMYK or RGB.

Here’s another representation:

Source: CMYK Printing vs RGB Explanation - What Is CMYK? - PrintNinja

And one last representation:

Source: RGB VS CMYK | Prepping your files for final print production

So, no matter what values you use, CMYK cannot reproduce those rich purples you can see on the screen.
CMYK and print media are always more subdued, as they are not projecting light into your eyes, only using reflected light.