QGIS. Clipping raster layer(asc) with vector layer results in missed color information

I have an imported asc file, then I generate a vector layer in order to clip part of the raster with that polygon shape.

The result is the correct clip but has lost the gray scale representing the height, it is only black.

This is the general view:

This is the original raster layer:

This is the "clipped" (clip raster by mask layer):

Any idea why the result misses pixel color information?

Thanks.