Lightroom colour picker tool
The colour picker tool in Lightroom is often overlooked, probably because it appears as a rectangular box with a cross in it and pretty non-descript looking and right at the bottom of the tools menu. It is available in the three local adjustment tools (the grad filter-the radial filter and the adjustment brush) and is used for adding colour or tone to the adjustment.
As you hover over the colour scale that appears when the box is clicked (see image) you simply move the eyedropper on to a colour you wish to use and click, now you can set the saturation o the colour by either using the slider at the bottom of the colour scale box, or you can (with the mouse click held down move the eye dropper up or down – increasing or decreasing the saturation of the chosen colour.
Now another way of getting a colour selected is to hold down the right mouse while in the box and (keeping the right button clicked down) move out of the box and onto the image and select a colour from within the image itself- this is most useful as it will ensure that the colour blends well with other colours in the image. You can also use this method and take the sample from any other image open on your screen at the time
The colour will be apparent in the area you have selected with the particular local adjustment tool used and by altering the saturation can be blended into the image nicely, further tweeks can be made with exposure/ temperature sliders etc