This will only work if you make a selection:
#target photoshop
var doc = activeDocument;
doc.colorSamplers.removeAll();
var pt = [doc.selection.bounds[0],doc.selection.bounds[1]];
var sampleColor = doc.colorSamplers.add(pt);
alert('Cyan: ' + sampleColor.color.cmyk.cyan +'\n' +'Magenta: ' + sampleColor.color.cmyk.magenta +'\n' +'Yellow: ' + sampleColor.color.cmyk.yellow +'\n' +'Black: ' + sampleColor.color.cmyk.black);