Is there a Windows PC equivalent to the color picker app found on Mac OS X called DigitalColor Meter?
I use ShareX (which is free and Open Source) as a screen grabber, it also has a "screen colour picker" in the Tools menu. It's quite nice because you can colour pick individual pixels.
It looks like this
I have no affiliation with ShareX. Their website is here: https://getsharex.com/
I've just discovered this project which seems simple and just works. Hit the Spacebar to save the current color or Ctrl+C to copy it directly as either HEX or RGB.
If you want to avoid installing anything, you can use Microsoft Paint. You can open a saved image in MS Paint, click the color picker (looks like an eye dropper), and click the part of the image you want the color for. Then go to Edit colors and you can see the RGB or Hue/Saturation/Lum. values.
If the color you want is not already saved as an image, you can use the built-in Snipping screenshot utility, then follow the steps above.
MS Paint enables zooming, so you can get down to the pixel you want.
There are some. The one I use is http://www.color-picker.de/
Note the original site above does not work
As of December 2018 the site seems to be gone, but it seems you can still view and download a version of V4 from The Internet Archive. https://web.archive.org/web/20181018075525/http://www.color-picker.de:80/
I was able to run the above downloaded version in a windows 10 sandbox, and it looks nice and simple, however does not allow single pixel and seems to average the pixels in a 3 x 3 area.
I came across Simplecolor recently, however it's not free.