I have an image where I need to determine the color of a certain group of pixels. At 72dpi on the screen I just can't be sure I'm selecting the right pixel. I'd like to zoom in to say 800% where each pixel in the image is just made 8 times bigger with no interpolation--the interpolation will mess up the colors.
Zooming in does not interpolate.
You can tell by the fact that the pixels have edges.
What version of Photoshop do you have? There was a version where the Eyedropper sampler tool didn't quite work right and it would pick up different colors in different parts of a pixel. But I'm pretty sure that's since been fixed.
If there is any blu8rriness/ resampling, that would be down to limitations in your hardware, so try and turn off OpenGL in the prefs. As Noel already said, zooming as such does not introduce any softness and uses simple pixel doubling.