By Nichole Swan
Are your scientific figures difficult to interpret if you view them with the colorblind simulators presented in “Creating Scientific Figures with Color in Mind”? Try out the following tools in Photoshop or ImageJ to modify the colors and patterns. If you have any questions, please contact me at email@example.com.
Converting Red to Magenta (for two-color red-green images)
- Open the Channels panel (Window → Channels).
- Select the Red channel and Select All (Ctrl/Cmd+A).
- Select the Blue channel and paste the contents into it (Ctrl/Cmd+V).
- Reselect the RGB channel.
Adding Patterns to Graphs
Graphs (such as bar graphs and pie charts) can be difficult for colorblind users to interpret. Patterns and textures can help users differentiate between sections of data. To add patterns or textures:
- Select elements of the same color. You can use the Magic Wand tool (for more on the Magic Wand tool, click here: https://helpx.adobe.com/photoshop/using/making-quick-selections.html#select_with_the_magic_wand_tool) To select multiple objects, press Shift with each click.
- With the same-colored objects selected, click on the adjustment layer button at the bottom of the Layers panel (image at right) or click Layer → New Fill Layer → Pattern.
- Choose a pattern or texture from the menu. You can then use Blending Modes (where the Normal” dropdown is in the image to the right) to blend the pattern with the color.
- Repeat for the other colors in your graph. Don’t forget to modify your chart legend, if you have one.
Converting Red to Magenta (or Green to Cyan)
This method uses Lookup Tables to replace the red or green color channels. However, not every image opened with ImageJ (or Fiji) has the channels separated. To do this:
- Go to Image → Color → Channels Tool.
- Select “Color” from the dropdown menu in the dialog box.
- Click OK when it asks to convert to multi-channel composite image.
- You should now notice a bar above your image indicating which channel you’re on, and a horizontal scroll bar below the image. The scroll bar moves you between red, green, and blue channels.
- With the red channel selected, go to Image → Lookup Table → Magenta.
- If you are converting green to cyan instead, make sure the green channel is selected and apply the Cyan Lookup Table.
- Don’t do both magenta and cyan; stick to either green/magenta or red/cyan.
One Last Note
Even after all your hard work ensuring that your figures are accessible to colorblind readers, you still might run into a snag. For example, this fluorescence microscopy image has three colors, and a simple one-color replacement won’t solve it perfectly.
As you can see above, differentiation would be difficult for those with deuteranopia, and even worse for those with protanopia. In this case, it’s worth investigating whether red/cyan would yield better results…
You can see here that for this particular three-color image, the red/cyan combination is easier to understand for colorblind readers.
Natalie Prigozhina (2015) CIL:48102, Homo sapiens, mammary epithelial cell. CIL. Dataset. https://doi.org/doi:10.7295/W9CIL48102