This problem is driving me crazy.
When I have any kind of layer, and I want to change the foreign or background color (with the color picker) I just cant.
When I click on the foreign or background color it automaticly selects the eyedropper tool, and I don't want this s**t to happend.
I assum you mena foreground, not foreign.
Try resetting your preferences, your color picker window could be going off screen and you are not seeing that window.
Immediately after booting Photoshop hold down 3 keys
Win - ctrl shift alt
Mac - shift option command