Is it possible to use the color range selection tool for a single layer? Right now it samples colors from all the layers to make the selection, so to select a color range in a specific layer, I have to make all the other layers invisible and then use the color range tool, which is really annoying. Any shortcuts?
Not a solution, but a workaround: you can make a single layer (or group) visible and hide all other layers by Alt-clicking the 'eye' in the layers palette. Make your selection. If you don't manually change any layer visibility, Photoshop will remember the visibility settings from before your Alt-click and restore them if you Alt-click on the visible layer's eye again.
Simply select the layer that you want to select the color, ctrl (cmd) + click on layer (or right click and "Select pixels") and go to Select > Color range; and you will only select the colors on one layer.