Paletted raster band rendering 

The paletted raster band renderer applies a single color to a single raster value. QGIS supports the loading of rasters with paletted colors stored within and changing the color assigned to the raster value. QGIS does not currently support the creation of color palettes for singleband rendering. However, existing QGIS layer style files (.qml) that contain palettes can be applied by clicking on the Load Style button in the layer properties.

As an example of a raster with a color palette stored within it, add SR_50M_alaska_nad.tif from the raster folder in the sample data, to the QGIS canvas and open the Symbology tab under Layer Properties. The following figure shows the Paletted / Unique Value renderer being applied to Band 1 (Gray) with a Color Ramp of Reds:

This is the output:

To change a color, double-click on a color in the Color ramp column to open the color picker.