Data Defined Labeling in QGIS
A useful and powerful way to define layer symbology and labels is using data-defined properties. While many of the options are self-explanatory, others require knowledge about the valid options.
Note: These options are currently only available for the “old” labeling under “Advanced” tab.
Valid options are: left, right, bottom, top, bottom_left, bottom_right, top_left, top_right
I successfully used the color names red, blue, green, black, yellow, and orange. Alternatively, you can enter color hex-codes: red = #ff0000