Tutorial

Color blindness is the decreased ability to see color or differences in color. Red-green color blindness affects up to 8% of males and 0.5% of females of Northern European descent. One of the things that designers should do is to ensure that graphical information can be understood and conveyed accurately to people with color vision deficiency. Photoshop provides soft-proof for color blindness Protanopia-type (reduced sensitivity to red) and Deuteranopia-type (reduced sensitivity to green).

How to soft-proof for color blindness

To soft proof your design for color blindness it is recommended to convert your document to RGB color mode because RGB mode is providing most accurate proof.

• Since you probably want to proof colors simultaneously for both, Protanopia-type and Deuteranopia-type color blindness it is recommended to create a new window from Window > Arrange > New window for [your document title]. 
• To see both windows (tabs) simultaneously go to View > Arrange > Tile All Vertically (or Horizontally). You can also use 2-up Horizontal/Vertical.
• Go to View > Proof Setup > Color Blindness > Protanopia-type.
• Switch to another tab (previously created using Window > Arrange > New window for [your document title]) then click on View > Proof Setup > Color Blindness > Deuteranopia-type.

Steps to soft-proof color in Photoshop for color blindness Protanopia-type and Deuteranopia-type with side by side view.

Product use in this tutorial:
Adobe Photoshop CC 2018

Reference:
About soft-proofing colors