Clone Tool doesn't work on an empty layer in Photoshop
Cloned pixels onto an empty layer must be above the image (background) layer and below all adjustments layers. It's important to check the Use All Layers checkbox on the Options bar for the Clone Stamp tool to work on another layer.
Also, be sure to turn off the visibility of all adjustment layers by clicking the eyeball to the left of the layer on the Layers palette. Doing this you will avoid the color cast of mixed pixels.