RGB vs CMYK: Getting the Right Colours in Print
Customers often say “it looked brighter on the phone”. They are right. Screens and printers make colour in different ways, and some colours that a screen can show simply cannot be printed with ink. Understanding RGB and CMYK lets you predict this and adjust the design before it reaches the printer.
Two ways of making colour
RGB (red, green, blue) is how screens work: they add light. Full red, green and blue light together make white, and very saturated colours such as neon pink, electric blue and bright orange are easy to show.
CMYK (cyan, magenta, yellow, black) is how printers work: ink absorbs light on white material. All the inks together make a dark brown-black, which is why a separate black (K) ink is used. The range of colours ink can produce, called the gamut, is smaller than a screen's, especially for bright greens, blues, purples and oranges.
What happens if you print an RGB file
Most print software converts RGB to CMYK automatically before printing. The conversion pulls out-of-gamut colours to the nearest printable colour, and you have no control over how. Saturated party colours, sunset gradients and glowing light effects are the usual victims: they come out flatter and sometimes with a different hue.
Converting in Photoshop
- Save a copy of your layered PSD first. Conversion changes the colour numbers of every layer.
- Ask your printer which colour profile they use. If they do not know, Coated FOGRA39 or U.S. Web Coated (SWOP) v2 are common defaults for offset; many flex printers simply ask for “CMYK”.
- Use Edit → Convert to Profile, choose the CMYK profile, set Intent to Relative Colorimetric or Perceptual and tick Black Point Compensation.
- If Photoshop asks about flattening or rasterising smart objects, choose Don't Flatten to keep layers.
- Compare with the original and fix colours that changed too much with Hue/Saturation or Curves adjustment layers.
Colours to watch
| Colour | What happens in print | What to do |
|---|---|---|
| Neon pink / magenta | Becomes a softer pink | Accept a deeper rose shade, or add contrast around it |
| Bright green | Turns olive or dull | Shift slightly toward yellow-green |
| Electric blue | Becomes purple-ish | Shift toward cyan, check the result in proof mode |
| Bright orange | Becomes brownish | Raise yellow, reduce black in the mix |
| Rich black text | Can blur if made of all four inks | Use 100% K only for small text |
When RGB is right
Keep RGB for anything that stays on a screen: WhatsApp invitations, Instagram and Facebook posts, status videos and website images. Converting these to CMYK only makes them duller. A good habit is to keep one RGB master for digital use and one CMYK copy for print. On TamilPSD each design page shows whether the file is RGB or CMYK, so you know which step you need.
Black for large areas
For large black backgrounds on offset print, a “rich black” such as C 40 M 30 Y 30 K 100 looks deeper than plain 100% K. Ask your printer before using it on flex, as some machines prefer plain black to avoid excessive ink.