Colour Simulations, A Desktop Application for Windows

User Guide

ColourSimulations version 1.2.5


The Colour Simulations application applies a colour transform to the underlying screen. Open the media of interest with the default windows application then simply place the ColourSimulations application window above the media to see the colour transformation. The colour transform is applied in real-time so the application can be used with video and also with games played in windowed mode.

Colour normal viewers should select 'Simulation' by pressing 'S' or selecting Simulation from the application menu. The window title will start with 'Simulation -'.

For users with colour vision deficiency a number of options are available to assist with colour discrimination, including the Daltonize algorithm, colour swaps and filters. RGB values at the mouse position are also displayed in the chromaticity diagram when the program is run in windowed mode.

The application menu can be accessed by right-clicking anywhere on the window and the main window moved and resized by dragging with the left mouse button. The hotkey 'Ctrl-F8' will toggle the colour transform on and off.

Colour Deficiency Type

The inherited forms of red-green colour-blindness can be simulated:

Press 'P' for Protanomalous/Protanope or select 'Protan' from the application menu.

Press 'D' for Deteranomalous/Deutanope or select 'Deutan' from the application menu.

Press 'T' for Tritanomalous/Tritanope or select 'Tritan' from the application menu.


Severity can be adjusted by scrolling the mouse-wheel or by pressing the + and - keys.

The range of severity goes from 0% (normal vision) to 100% (dichromat).

For Protanomalous vision the severity range is of the order 75% to 95% (*).

For Deuteranomalous vision the severity range is of the order 55% to 95% (*).

(* Approximate ranges based on known variations of photopigment molecules)


The simulation option simulates colour vision deficiency for colour normal viewers.

Press 'S' or select Simulation from the application menu. The window title will start with 'Simulation -'.

The simulation algorithm reduces the colour space to the blue-yellow axis while preserving the black-white achromatic scale. Confusion lines are consistent with the chromaticity xy confusion points of [0.753,0.247] for Protan deficiency and [1.00,0.00] for Deutan deficiency.

A Tritan deficiency simulation is included with xy confusion point [0.17,0.00]. Note there are limitations of this simulation: firstly the simulation places colours outside the available RGB space that can be displayed by a computer monitor, hence some colours are compromised; secondly the colour simulations application uses microsoft's magnificaiton api to apply a colour transform, this limits the transformation to a single conversion matrix which compromises the colour perception for Tritan deficiency. The application can be used to give an indication of colour confusion (useful for UI design for example), for a better indication of Tritan deficiency colour perception the free program 'Coblis' is recommended.


The Daltonize algorithm ( assists viewers with colour vision deficiency.

Press 'A' or select Daltonize from the application menu.

The algorithm applies contrast in proportion to the missing colour components: Red will get lighter and the other colours darker. The missing colour components are estimated by the simulation algorithm, here the mouse-wheel can be used to control the level of correction: note there is no right or wrong correction, the user can adjust the level of correction to suite the image, selecting an appropriate level of correction according to the detail revealed in the image.

Inverse Transform

The inverse transform is of interest to anomalous viewers (as opposed to dichromats) as it give an indication of normal colour perception for colour deficient viewers. Note the range of colours that can be successfully transformed is very small, depending on the severity of the observer. Users should start with 0% severity and move up. Colours will quickly become saturated as the transformed colours go outside of the colour space that can be displayed.

Colour Swaps and Filters

Swapping red and blue is another tool for the colour deficient viewer to discriminate confused colours. This option does have the issue of introducing other colour confusions so its usefulness is very dependant on the image.

Swaping red and blue is selected from the application menu and the ammount of colour swapped controlled with the mouse wheel from 0% to 100%.

Other colour swaps can be selected from the application menu: Other colour effects->Colour Swap

Colour filters may also be useful, from the application menu: Other colour effects->Colour Filter

RGB Cube

The RGB cube is a visual display of the colour space.

Press 'R' to display the cube or from the application menu select: Colour space Window-> RGB Cube

The cube can be rotated with the left mouse-button

As the severity of the colour vision deficiency is increased the cube is tranformed to show the available colour space of the colour deficient viewer. Note the outline of the colour-normal cube is always displayed for reference.

Chromaticity Diagram

The CIE xy Chromaticity diagram is another visual display of the colour space.

Press 'C' to display the diagram or from the application menu select: Colour space Window-> Chromaticity diagram

The curve of spectral colours is shown together with the RGB colour space displayed by a typical computer monitor.

The RGB colour-normal triangle outline is always shown for reference while the colour gamut reduces with severity.

The mouse-over chroma and RGB values are displayed here.

Photoreceptor response curves

The Photoreceptor response curves show the wavelength absorption of the S, M and L cone cells in the retina.

Press 'E' to display the curves or from the application menu select: Colour space Window-> Photoreceptor response curves

As the severity is increased the reduced separation of the M and L cone response can be visualized.

Blue Light Block

The blue light block elimiates blue colour output and reduces green, this is to reduce stimulation of the circadian rythym that can affect sleep patterns. The mouse wheel provides a brightness control in this mode.

Other Colour Effects

These colour transforms are provided as utilities, select from the appliction menu:






Hit Transparent Mode

This option allows the user to work on an underlying document or application.

Press H or from the application menu select: View Options-> Hit Transparent

A control window opens giving the user access to the application menu (right-click) and the option to exit hit-transparent mode.

Full screen mode

Selecting fullscreen applies the colour transform to the entire desktop. The program icon moves to the systray (notification) area and auto-start is enabled. Left-clicking on the systray icon toggles the control window visibility and right-clicking provides options to exit or toggle the transform off. Exiting the program will disable auto-start.

Screen Capture

Press Ctrl-C to copy an image to the system clipboard.

The captured image gives the tranformed image displayed in the application window.

For fine positioning of the window use the arrow keys for pixel position adjustment and shift-arrow keys for height/width adjustment.