RGB: working with light
RGB describes red, green and blue components. It is commonly used in screen-based work, where emitted light combines to produce the displayed colour. Increasing all components toward their maximum in a typical RGB representation moves toward white. The exact colour represented by a set of values depends on the colour space and display conditions, so RGB numbers need context.
CMYK: planning for print
CMYK describes cyan, magenta, yellow and black components used in many print workflows. Ink changes the light reflected from a surface. Paper, ink, the printing process and the chosen profile affect the result. A vivid screen colour may fall outside the range that a particular printing process can reproduce. Do not expect a simple conversion to make every colour match.
HSL: adjusting colour intuitively
HSL describes hue, saturation and lightness and is derived from RGB. It can make some adjustments easier to discuss: change the hue while exploring saturation or lightness separately. HSL lightness is not a guarantee of equal perceived brightness across hues. Two colours with the same lightness number can still appear different in brightness and contrast.
Distinguish a model from a colour space
A model describes a way of organising components; a colour space adds a particular interpretation of those components. For example, sRGB is an RGB colour space. This distinction matters when moving between devices or applications. When preparing files for someone else, use their requested profile and workflow instead of assuming that every application interprets a colour in the same way.
Choose for the output
For a screen exercise, start in an appropriate RGB workflow. For a printed piece, ask for the printer’s requirements before final export and review a proof where practical. Compare the same design on screen and on paper under reasonable viewing conditions. Record what changes, such as a loss of intensity or a shift in a neutral, rather than promising an exact match from memory.
YOUR TURN / ORIGINAL PRACTICE
Make it your own.
Choose a small palette in a digital drawing tool. Record its RGB and HSL values, then inspect a CMYK conversion if your software supports it. Identify any visible changes and write down the intended output: screen or a named print process. Treat the conversion as an observation, not a proof of final print appearance.
Review your work
- Have you distinguished emitted light from ink on a surface?
- Have you recorded the colour space where available?
- Can you explain why the output medium affects your choices?
Further reading: W3C CSS Color specification ↗ for digital colour models and spaces.