Pickard
Pickard is an open source color selection tool, licensed under the GNU General Public License, that has many features of the color pickers you can find in high-level image processing applications (like Photoshop, Paint Shop Pro or GIMP), its features includes:
Spectrum color selection
Eyedrop color selection
Multiple color spaces support (RGB, HSL, CMY, YUV)
Multiple color string formats (HTML, Delphi, Visual Basic, C++, SSA, ASS)
Screen magnifier with variable zoom level (from 1:1 to 1:20)
- "Stay on top" functionality