GreyColorViewer was designed to help with total color blindness. Being color blind can be problematic in a world where color is used to link and separate. GCV highlights instances of a color so it becomes visible from the other shades of grey.
It sits in the system tray until clicked, then screen captures the primary desktop. You then click on the capture overlay to highlight similar instances of color. Also provides RGB values and a common name for the selected color.
There is no installer, just a single, portable .EXE to run. GCV is free, open source, programmed in C# .NET It can also run on Linux, see instructions below.
Examples of it in action:
For Linux Users
The tool will run using Mono, however you need the full mono package: sudo apt-get mono-complete
Ubuntu with its Unity desktop only allows approved applications to show a tray icon: gsettings set com.canonical.Unity.Panel systray-whitelist "['GreyColorViewer']"
Aside from the tool, the C Sharp source code also includes a couple of useful helper classes for safe, fast, bitmap pixel manipulation, using LockBits / UnlockBits / Marshal.Copy and also finding the closest color match using HSL and euclidean distances.