The RGB mosaic system is an automatic tool to generate a mosaic over the Alps that provides the last SENTINEL-2 color images available, with a cloud coverage of less than 30% of the entire scene. The system is composed of open source software for processing and visualization tasks and the Data Exchange Server tool (DES) tool, developed by Eurac Research, to automatize server-based tasks. The processing of the images uses a python code and GDAL libraries to estimate cloud and no-data coverage in each tile and to optimize the images for a better visualization. The DES is useful to automatize images downloading, to run the processing tasks in the right order and to update the mosaic and metadata when the processing is over. The result is shared through a WMS (Web Map Service) layer and in a web page for a quick look.