Learn to control and manage the White Balance tool and loupe in Lightroom
The White Balance Loupe shows you information about the color under the cursor. Across the bottom you will see the percent of Red, Green and Blue in the current selection. If the color is neutral then all values will be equal.
If you un-check the Auto Dismiss check-box at the foot of the preview, the Loupe will stay visible allowing you to click multiple times to find a good place to use to adjust the white balance. I think this setting should have been set to be not selected by default – it just makes white balance corrections so much easier because, let’s face it, none of us ever get it right first time every time!