on it to permit to discuss more easier on changes and new planings about circulation, new amenagements, bike way networks etc.?
There is not only one OSM map. Use an OSM-based map which is greyscale or make it greyscale in your own postprocessing.
You can use those premade map styles in your web/software application (whatever it is, you do not name it): see section “toner” on http://maps.stamen.com/ or http://mc.bbbike.org/mc/?lon=13.38885&lat=52.51703&zoom=11&num=4&mt0=mapnik-bw&mt1=esri-gray&mt2=osm-roads-greyscale&mt3=toner . Always obey the copyrights and tile server usage restrictions, depending on your usecase.