Different background color between basecamp and Garmin device

hello everybody

I am trying to build OSM based maps for my Garmin etrex 35t but facing a strange issue: while the background in the Basecamp app (on Mac) is properly displayed in white (as defined in the TYP file), on the device the color becomes blue.

Any idea why the color is replaced on the device?

thanks a lot in advance and best regards

Maybe something is missing in your generate-sea parameters?

--generate-sea= land-tag=TAG=VAL

Tag to use for land polygons (default natural=land)

I use natural=background for tag=value and in the polygon file you can specify a garmin typ for this background polygon.