If I create a product for NDVI using GPF.createProduct() and write the product to GeoTiff or PNG, how can I associate a colour map to it? Thank you great work
Based on your using GPF.createProduct(), I think you are using python packages offered by snap. SNAP seems not offering any direct method to export a “color map” to show spatial distributions for NDVI. To solve this you can use GDAL (another very famous geospatial library).
See this post or google gdal_dem for more information: https://gis.stackexchange.com/questions/104196/how-to-add-a-color-table-to-a-one-band-tiff-using-gdal