On this page

1. Colour Choice

The Colour Choice controls are divided into 2 sections (foreground & background) each has 3 ways to choose a colour to test.

Colour choice user interface


Colour pallet(s) accessed via a select box. Use this to help you test and choose suitable colour combinations.

Colour pallet

The bottom (smaller) colour pallet consists of 10 shades of the currently selected base colour, located top-left, at varying degrees of opacity. The top row emulates opacity over a white background, the bottom over black . The opacity values are 100% opaque, 75%, 50%, 25% and 10% on the top row. The bottom row begins at 85% rather than 100% and continues on as the first.

This pallet is useful for testing lighter and darker shades of the base colour, which may improve the visibility of the colour combination being tested.

Note: This feature was inspired by the Color Palette Creator.


Input of a colour value (in Hexadecimal format) into a text box. Useful if you have access to the Hex values of colours you want to check.

Hex value input box


Sampling of a colour from a web page (or anywhere else on the screen) using a magnifying colour sampler.  

Colour sampler button

Useful for quickly sampling, checking and obtaining the hex values of colours. Once the colour sampler button is selected a magnified area will appear around the cursor. The colour of the content under the tip of the cursor will appear in the colour pallet select box

Once a colour is chosen with the colour sampler (left mouse click or 'enter' key) its hex value will appear in the 'hex value' text box and the results section will be updated to reflect the brightness and colour differences for the currently selected colour combination.

Note: For fine control of the cursor use the arrow keys.

Example of the magnified area around the cursor that occurs when the colour sampler is activated. The colour under the cursor tip appears in the colour pallet select box

2. Results

The Results section is divided into summary results and full results.

The 'Summary Results' indicate a value for both brightness and colour difference. 

Summary results

If both pass the check this is indicated with a tick. If either fail this is indicated with a cross.

The 'Full Results' displays the values for each of the checks and what the pass/fail criteria are and indicates whether the contrast was found to be sufficient/insufficient.

Note: The text of the summary and full results can be selected and copied.

The results section of the contrast analyser

3. Colour Blindness Results

Selecting the 'also show contrast results for colour blindness' check box will display summary results for 'normal vision' and 3 types of colour blindness (Protanopia, Deuteranopia, Tritanopia) 

Display of colour blindess results

Note: The method of determining the colour value transformations for the 3 types of colour deficiency is from an algorithm described by Hans Brettel, Francoise Vienot and John Mollon in a paper which appeared in the Journal of the Optical Society of America V14, #10 pp2647.

Acknowledgements to the kind people at Vischeck who allowed us access to the source code of their implementation of the Brettel algorithm.

4. Options & Help Menus

Selecting the 'always on top' menu item will keep the CCA window on top of all other windows that are open. Selecting 'font' menu item opens a dialog box that allows you to modify the font used for the text labels and content of the CCA

Note: selecting some font types or sizes can result in clipping of text content. 

Options menu

Selecting the "help" Menu item  will open the CCAdocumentation web page in a browser window.

Help menu

Note: you will need to be connected to the internet to access the documentation.

Keyboard Access Keys

Colour Contrast Analyser Access keys
Function Key(s)
open foreground colour pallet(s) F9
open background colour pallets(s) F10
move through colour pallets arrow keys or the tab key
activate foreground colour sampler F11
activate background colour sampler F12
move colour sampler arrow keys
choose colour in sampler or pallet Enter