Sim Daltonism is a free, open-source Mac and iOS app that simulates color blindness live: drag a filter window over any part of the screen (Mac) or point the camera at anything (iOS) to see it through a color-blind lens.
It covers red-green, blue-yellow, and full monochromacy variants, and because the Mac version filters whatever's underneath the window in real time, an entire design can be checked in its actual working context, not a static exported screenshot.
Designers who want to check a live design or physical scene for color-blind accessibility on the spot, on Mac or through an iPhone camera, not merely a single uploaded image.
The simulation is an approximation. Color blindness varies significantly between individuals, so treat results as a useful check, not a guarantee of how any specific person will see the design.
